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https://github.com/apple/swift.git
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764 lines
18 KiB
Swift
764 lines
18 KiB
Swift
//===--- Prims.swift ------------------------------------------------------===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2014 - 2021 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See https://swift.org/LICENSE.txt for license information
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// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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// The test implements Prim's algorithm for minimum spanning tree building.
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// http://en.wikipedia.org/wiki/Prim%27s_algorithm
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// This class implements array-based heap (priority queue).
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// It is used to store edges from nodes in spanning tree to nodes outside of it.
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// We are interested only in the edges with the smallest costs, so if there are
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// several edges pointing to the same node, we keep only one from them. Thus,
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// it is enough to record this node instead.
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// We maintain a map (node index in graph)->(node index in heap) to be able to
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// update the heap fast when we add a new node to the tree.
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import TestsUtils
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public let benchmarks = [
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BenchmarkInfo(
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name: "Prims",
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runFunction: run_Prims,
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tags: [.validation, .algorithm],
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legacyFactor: 5),
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]
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class PriorityQueue {
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final var heap: Array<EdgeCost>
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final var graphIndexToHeapIndexMap: Array<Int?>
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// Create heap for graph with NUM nodes.
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init(Num: Int) {
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heap = Array<EdgeCost>()
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graphIndexToHeapIndexMap = Array<Int?>(repeating:nil, count: Num)
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}
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func isEmpty() -> Bool {
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return heap.isEmpty
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}
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// Insert element N to heap, maintaining the heap property.
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func insert(_ n: EdgeCost) {
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let ind: Int = heap.count
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heap.append(n)
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graphIndexToHeapIndexMap[n.to] = heap.count - 1
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bubbleUp(ind)
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}
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// Insert element N if in's not in the heap, or update its cost if the new
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// value is less than the existing one.
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func insertOrUpdate(_ n: EdgeCost) {
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let id = n.to
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let c = n.cost
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if let ind = graphIndexToHeapIndexMap[id] {
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if heap[ind].cost <= c {
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// We don't need an edge with a bigger cost
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return
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}
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heap[ind].cost = c
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heap[ind].from = n.from
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bubbleUp(ind)
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} else {
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insert(n)
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}
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}
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// Restore heap property by moving element at index IND up.
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// This is needed after insertion, and after decreasing an element's cost.
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func bubbleUp(_ ind: Int) {
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var ind = ind
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let c = heap[ind].cost
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while (ind != 0) {
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let p = getParentIndex(ind)
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if heap[p].cost > c {
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swap(p, with: ind)
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ind = p
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} else {
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break
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}
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}
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}
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// Pop minimum element from heap and restore the heap property after that.
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func pop() -> EdgeCost? {
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if (heap.isEmpty) {
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return nil
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}
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swap(0, with:heap.count-1)
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let r = heap.removeLast()
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graphIndexToHeapIndexMap[r.to] = nil
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bubbleDown(0)
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return r
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}
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// Restore heap property by moving element at index IND down.
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// This is needed after removing an element, and after increasing an
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// element's cost.
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func bubbleDown(_ ind: Int) {
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var ind = ind
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let n = heap.count
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while (ind < n) {
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let l = getLeftChildIndex(ind)
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let r = getRightChildIndex(ind)
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if (l >= n) {
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break
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}
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var min: Int
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if (r < n && heap[r].cost < heap[l].cost) {
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min = r
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} else {
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min = l
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}
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if (heap[ind].cost <= heap[min].cost) {
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break
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}
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swap(ind, with: min)
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ind = min
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}
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}
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// Swaps elements I and J in the heap and correspondingly updates
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// graphIndexToHeapIndexMap.
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func swap(_ i: Int, with j : Int) {
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if (i == j) {
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return
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}
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(heap[i], heap[j]) = (heap[j], heap[i])
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let (i2, j2) = (heap[i].to, heap[j].to)
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(graphIndexToHeapIndexMap[i2], graphIndexToHeapIndexMap[j2]) =
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(graphIndexToHeapIndexMap[j2], graphIndexToHeapIndexMap[i2])
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}
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// Dumps the heap.
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func dump() {
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print("QUEUE")
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for nodeCost in heap {
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let to: Int = nodeCost.to
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let from: Int = nodeCost.from
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let cost: Double = nodeCost.cost
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print("(\(from)->\(to), \(cost))")
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}
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}
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func getLeftChildIndex(_ index : Int) -> Int {
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return index*2 + 1
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}
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func getRightChildIndex(_ index : Int) -> Int {
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return (index + 1)*2
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}
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func getParentIndex(_ childIndex : Int) -> Int {
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return (childIndex - 1)/2
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}
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}
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struct GraphNode {
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var id: Int
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var adjList: Array<Int>
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init(i : Int) {
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id = i
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adjList = Array<Int>()
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}
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}
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struct EdgeCost {
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var to: Int
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var cost: Double
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var from: Int
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}
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struct Edge : Equatable {
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var start: Int
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var end: Int
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}
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func ==(lhs: Edge, rhs: Edge) -> Bool {
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return lhs.start == rhs.start && lhs.end == rhs.end
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}
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extension Edge : Hashable {
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func hash(into hasher: inout Hasher) {
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hasher.combine(start)
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hasher.combine(end)
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}
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}
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func prims(_ graph : Array<GraphNode>, _ fun : (Int, Int) -> Double) -> Array<Int?> {
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var treeEdges = Array<Int?>(repeating:nil, count:graph.count)
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let queue = PriorityQueue(Num:graph.count)
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// Make the minimum spanning tree root its own parent for simplicity.
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queue.insert(EdgeCost(to: 0, cost: 0.0, from: 0))
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// Take an element with the smallest cost from the queue and add its
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// neighbors to the queue if their cost was updated
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while !queue.isEmpty() {
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// Add an edge with minimum cost to the spanning tree
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let e = queue.pop()!
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let newnode = e.to
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// Add record about the edge newnode->e.from to treeEdges
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treeEdges[newnode] = e.from
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// Check all adjacent nodes and add edges, ending outside the tree, to the
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// queue. If the queue already contains an edge to an adjacent node, we
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// replace existing one with the new one in case the new one costs less.
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for adjNodeIndex in graph[newnode].adjList {
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if treeEdges[adjNodeIndex] != nil {
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continue
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}
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let newcost = fun(newnode, graph[adjNodeIndex].id)
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queue.insertOrUpdate(EdgeCost(to: adjNodeIndex, cost: newcost, from: newnode))
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}
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}
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return treeEdges
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}
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@inline(never)
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public func run_Prims(_ n: Int) {
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for _ in 1...n {
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let nodes : [Int] = [ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
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13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28,
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29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44,
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45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60,
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61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76,
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77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92,
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93, 94, 95, 96, 97, 98, 99 ]
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// Prim's algorithm is designed for undirected graphs.
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// Due to that, in our set all the edges are paired, i.e. for any
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// edge (start, end, C) there is also an edge (end, start, C).
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let edges : [(Int, Int, Double)] = [
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(26, 47, 921),
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(20, 25, 971),
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(92, 59, 250),
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(33, 55, 1391),
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(78, 39, 313),
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(7, 25, 637),
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(18, 19, 1817),
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(33, 41, 993),
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(64, 41, 926),
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(88, 86, 574),
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(93, 15, 1462),
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(86, 33, 1649),
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(37, 35, 841),
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(98, 51, 1160),
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(15, 30, 1125),
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(65, 78, 1052),
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(58, 12, 1273),
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(12, 17, 285),
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(45, 61, 1608),
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(75, 53, 545),
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(99, 48, 410),
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(97, 0, 1303),
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(48, 17, 1807),
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(1, 54, 1491),
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(15, 34, 807),
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(94, 98, 646),
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(12, 69, 136),
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(65, 11, 983),
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(63, 83, 1604),
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(78, 89, 1828),
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(61, 63, 845),
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(18, 36, 1626),
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(68, 52, 1324),
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(14, 50, 690),
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(3, 11, 943),
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(21, 68, 914),
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(19, 44, 1762),
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(85, 80, 270),
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(59, 92, 250),
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(86, 84, 1431),
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(19, 18, 1817),
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(52, 68, 1324),
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(16, 29, 1108),
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(36, 80, 395),
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(67, 18, 803),
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(63, 88, 1717),
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(68, 21, 914),
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(75, 82, 306),
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(49, 82, 1292),
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(73, 45, 1876),
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(89, 82, 409),
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(45, 47, 272),
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(22, 83, 597),
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(61, 12, 1791),
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(44, 68, 1229),
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(50, 51, 917),
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(14, 53, 355),
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(77, 41, 138),
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(54, 21, 1870),
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(93, 70, 1582),
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(76, 2, 1658),
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(83, 73, 1162),
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(6, 1, 482),
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(11, 65, 983),
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(81, 90, 1024),
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(19, 1, 970),
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(8, 58, 1131),
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(60, 42, 477),
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(86, 29, 258),
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(69, 59, 903),
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(34, 15, 807),
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(37, 2, 1451),
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(7, 73, 754),
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(47, 86, 184),
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(67, 17, 449),
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(18, 67, 803),
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(25, 4, 595),
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(3, 31, 1337),
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(64, 31, 1928),
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(9, 43, 237),
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(83, 63, 1604),
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(47, 45, 272),
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(86, 88, 574),
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(87, 74, 934),
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(98, 94, 646),
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(20, 1, 642),
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(26, 92, 1344),
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(18, 17, 565),
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(47, 11, 595),
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(10, 59, 1558),
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(2, 76, 1658),
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(77, 74, 1277),
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(42, 60, 477),
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(80, 36, 395),
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(35, 23, 589),
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(50, 37, 203),
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(6, 96, 481),
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(78, 65, 1052),
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(1, 52, 127),
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(65, 23, 1932),
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(46, 51, 213),
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(59, 89, 89),
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(15, 93, 1462),
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(69, 3, 1305),
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(17, 37, 1177),
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(30, 3, 193),
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(9, 15, 818),
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(75, 95, 977),
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(86, 47, 184),
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(10, 12, 1736),
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(80, 27, 1010),
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(12, 10, 1736),
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(86, 1, 1958),
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(60, 12, 1240),
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(43, 71, 683),
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(91, 65, 1519),
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(33, 86, 1649),
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(62, 26, 1773),
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(1, 13, 1187),
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(2, 10, 1018),
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(91, 29, 351),
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(69, 12, 136),
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(43, 9, 237),
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(29, 86, 258),
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(17, 48, 1807),
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(31, 64, 1928),
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(68, 61, 1936),
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(76, 38, 1724),
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(1, 6, 482),
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(53, 14, 355),
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(51, 50, 917),
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(54, 13, 815),
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(19, 29, 883),
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(35, 87, 974),
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(70, 96, 511),
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(23, 35, 589),
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(39, 69, 1588),
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(93, 73, 1093),
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(13, 73, 435),
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(5, 60, 1619),
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(42, 41, 1523),
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(66, 58, 1596),
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(1, 67, 431),
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(17, 67, 449),
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(30, 95, 906),
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(71, 43, 683),
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(5, 87, 190),
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(12, 78, 891),
|
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(30, 97, 402),
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(28, 17, 1131),
|
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(7, 97, 1356),
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(58, 66, 1596),
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(20, 37, 1294),
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(73, 76, 514),
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(54, 8, 613),
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(68, 35, 1252),
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(92, 32, 701),
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(3, 90, 652),
|
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(99, 46, 1576),
|
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(13, 54, 815),
|
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(20, 87, 1390),
|
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(36, 18, 1626),
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(51, 26, 1146),
|
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(2, 23, 581),
|
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(29, 7, 1558),
|
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(88, 59, 173),
|
|
(17, 1, 1071),
|
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(37, 49, 1011),
|
|
(18, 6, 696),
|
|
(88, 33, 225),
|
|
(58, 38, 802),
|
|
(87, 50, 1744),
|
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(29, 91, 351),
|
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(6, 71, 1053),
|
|
(45, 24, 1720),
|
|
(65, 91, 1519),
|
|
(37, 50, 203),
|
|
(11, 3, 943),
|
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(72, 65, 1330),
|
|
(45, 50, 339),
|
|
(25, 20, 971),
|
|
(15, 9, 818),
|
|
(14, 54, 1353),
|
|
(69, 95, 393),
|
|
(8, 66, 1213),
|
|
(52, 2, 1608),
|
|
(50, 14, 690),
|
|
(50, 45, 339),
|
|
(1, 37, 1273),
|
|
(45, 93, 1650),
|
|
(39, 78, 313),
|
|
(1, 86, 1958),
|
|
(17, 28, 1131),
|
|
(35, 33, 1667),
|
|
(23, 2, 581),
|
|
(51, 66, 245),
|
|
(17, 54, 924),
|
|
(41, 49, 1629),
|
|
(60, 5, 1619),
|
|
(56, 93, 1110),
|
|
(96, 13, 461),
|
|
(25, 7, 637),
|
|
(11, 69, 370),
|
|
(90, 3, 652),
|
|
(39, 71, 1485),
|
|
(65, 51, 1529),
|
|
(20, 6, 1414),
|
|
(80, 85, 270),
|
|
(73, 83, 1162),
|
|
(0, 97, 1303),
|
|
(13, 33, 826),
|
|
(29, 71, 1788),
|
|
(33, 12, 461),
|
|
(12, 58, 1273),
|
|
(69, 39, 1588),
|
|
(67, 75, 1504),
|
|
(87, 20, 1390),
|
|
(88, 97, 526),
|
|
(33, 88, 225),
|
|
(95, 69, 393),
|
|
(2, 52, 1608),
|
|
(5, 25, 719),
|
|
(34, 78, 510),
|
|
(53, 99, 1074),
|
|
(33, 35, 1667),
|
|
(57, 30, 361),
|
|
(87, 58, 1574),
|
|
(13, 90, 1030),
|
|
(79, 74, 91),
|
|
(4, 86, 1107),
|
|
(64, 94, 1609),
|
|
(11, 12, 167),
|
|
(30, 45, 272),
|
|
(47, 91, 561),
|
|
(37, 17, 1177),
|
|
(77, 49, 883),
|
|
(88, 23, 1747),
|
|
(70, 80, 995),
|
|
(62, 77, 907),
|
|
(18, 4, 371),
|
|
(73, 93, 1093),
|
|
(11, 47, 595),
|
|
(44, 23, 1990),
|
|
(20, 0, 512),
|
|
(3, 69, 1305),
|
|
(82, 3, 1815),
|
|
(20, 88, 368),
|
|
(44, 45, 364),
|
|
(26, 51, 1146),
|
|
(7, 65, 349),
|
|
(71, 39, 1485),
|
|
(56, 88, 1954),
|
|
(94, 69, 1397),
|
|
(12, 28, 544),
|
|
(95, 75, 977),
|
|
(32, 90, 789),
|
|
(53, 1, 772),
|
|
(54, 14, 1353),
|
|
(49, 77, 883),
|
|
(92, 26, 1344),
|
|
(17, 18, 565),
|
|
(97, 88, 526),
|
|
(48, 80, 1203),
|
|
(90, 32, 789),
|
|
(71, 6, 1053),
|
|
(87, 35, 974),
|
|
(55, 90, 1808),
|
|
(12, 61, 1791),
|
|
(1, 96, 328),
|
|
(63, 10, 1681),
|
|
(76, 34, 871),
|
|
(41, 64, 926),
|
|
(42, 97, 482),
|
|
(25, 5, 719),
|
|
(23, 65, 1932),
|
|
(54, 1, 1491),
|
|
(28, 12, 544),
|
|
(89, 10, 108),
|
|
(27, 33, 143),
|
|
(67, 1, 431),
|
|
(32, 45, 52),
|
|
(79, 33, 1871),
|
|
(6, 55, 717),
|
|
(10, 58, 459),
|
|
(67, 39, 393),
|
|
(10, 4, 1808),
|
|
(96, 6, 481),
|
|
(1, 19, 970),
|
|
(97, 7, 1356),
|
|
(29, 16, 1108),
|
|
(1, 53, 772),
|
|
(30, 15, 1125),
|
|
(4, 6, 634),
|
|
(6, 20, 1414),
|
|
(88, 56, 1954),
|
|
(87, 64, 1950),
|
|
(34, 76, 871),
|
|
(17, 12, 285),
|
|
(55, 59, 321),
|
|
(61, 68, 1936),
|
|
(50, 87, 1744),
|
|
(84, 44, 952),
|
|
(41, 33, 993),
|
|
(59, 18, 1352),
|
|
(33, 27, 143),
|
|
(38, 32, 1210),
|
|
(55, 70, 1264),
|
|
(38, 58, 802),
|
|
(1, 20, 642),
|
|
(73, 13, 435),
|
|
(80, 48, 1203),
|
|
(94, 64, 1609),
|
|
(38, 28, 414),
|
|
(73, 23, 1113),
|
|
(78, 12, 891),
|
|
(26, 62, 1773),
|
|
(87, 43, 579),
|
|
(53, 6, 95),
|
|
(59, 95, 285),
|
|
(88, 63, 1717),
|
|
(17, 5, 633),
|
|
(66, 8, 1213),
|
|
(41, 42, 1523),
|
|
(83, 22, 597),
|
|
(95, 30, 906),
|
|
(51, 65, 1529),
|
|
(17, 49, 1727),
|
|
(64, 87, 1950),
|
|
(86, 4, 1107),
|
|
(37, 98, 1102),
|
|
(32, 92, 701),
|
|
(60, 94, 198),
|
|
(73, 98, 1749),
|
|
(4, 18, 371),
|
|
(96, 70, 511),
|
|
(7, 29, 1558),
|
|
(35, 37, 841),
|
|
(27, 64, 384),
|
|
(12, 33, 461),
|
|
(36, 38, 529),
|
|
(69, 16, 1183),
|
|
(91, 47, 561),
|
|
(85, 29, 1676),
|
|
(3, 82, 1815),
|
|
(69, 58, 1579),
|
|
(93, 45, 1650),
|
|
(97, 42, 482),
|
|
(37, 1, 1273),
|
|
(61, 4, 543),
|
|
(96, 1, 328),
|
|
(26, 0, 1993),
|
|
(70, 64, 878),
|
|
(3, 30, 193),
|
|
(58, 69, 1579),
|
|
(4, 25, 595),
|
|
(31, 3, 1337),
|
|
(55, 6, 717),
|
|
(39, 67, 393),
|
|
(78, 34, 510),
|
|
(75, 67, 1504),
|
|
(6, 53, 95),
|
|
(51, 79, 175),
|
|
(28, 91, 1040),
|
|
(89, 78, 1828),
|
|
(74, 93, 1587),
|
|
(45, 32, 52),
|
|
(10, 2, 1018),
|
|
(49, 37, 1011),
|
|
(63, 61, 845),
|
|
(0, 20, 512),
|
|
(1, 17, 1071),
|
|
(99, 53, 1074),
|
|
(37, 20, 1294),
|
|
(10, 89, 108),
|
|
(33, 92, 946),
|
|
(23, 73, 1113),
|
|
(23, 88, 1747),
|
|
(49, 17, 1727),
|
|
(88, 20, 368),
|
|
(21, 54, 1870),
|
|
(70, 93, 1582),
|
|
(59, 88, 173),
|
|
(32, 38, 1210),
|
|
(89, 59, 89),
|
|
(23, 44, 1990),
|
|
(38, 76, 1724),
|
|
(30, 57, 361),
|
|
(94, 60, 198),
|
|
(59, 10, 1558),
|
|
(55, 64, 1996),
|
|
(12, 11, 167),
|
|
(36, 24, 1801),
|
|
(97, 30, 402),
|
|
(52, 1, 127),
|
|
(58, 87, 1574),
|
|
(54, 17, 924),
|
|
(93, 74, 1587),
|
|
(24, 36, 1801),
|
|
(2, 37, 1451),
|
|
(91, 28, 1040),
|
|
(59, 55, 321),
|
|
(69, 11, 370),
|
|
(8, 54, 613),
|
|
(29, 85, 1676),
|
|
(44, 19, 1762),
|
|
(74, 79, 91),
|
|
(93, 56, 1110),
|
|
(58, 10, 459),
|
|
(41, 50, 1559),
|
|
(66, 51, 245),
|
|
(80, 19, 1838),
|
|
(33, 79, 1871),
|
|
(76, 73, 514),
|
|
(98, 37, 1102),
|
|
(45, 44, 364),
|
|
(16, 69, 1183),
|
|
(49, 41, 1629),
|
|
(19, 80, 1838),
|
|
(71, 57, 500),
|
|
(6, 4, 634),
|
|
(64, 27, 384),
|
|
(84, 86, 1431),
|
|
(5, 17, 633),
|
|
(96, 88, 334),
|
|
(87, 5, 190),
|
|
(70, 21, 1619),
|
|
(55, 33, 1391),
|
|
(10, 63, 1681),
|
|
(11, 62, 1339),
|
|
(33, 13, 826),
|
|
(64, 70, 878),
|
|
(65, 72, 1330),
|
|
(70, 55, 1264),
|
|
(64, 55, 1996),
|
|
(50, 41, 1559),
|
|
(46, 99, 1576),
|
|
(88, 96, 334),
|
|
(51, 20, 868),
|
|
(73, 7, 754),
|
|
(80, 70, 995),
|
|
(44, 84, 952),
|
|
(29, 19, 883),
|
|
(59, 69, 903),
|
|
(57, 53, 1575),
|
|
(90, 13, 1030),
|
|
(28, 38, 414),
|
|
(12, 60, 1240),
|
|
(85, 58, 573),
|
|
(90, 55, 1808),
|
|
(4, 10, 1808),
|
|
(68, 44, 1229),
|
|
(92, 33, 946),
|
|
(90, 81, 1024),
|
|
(53, 75, 545),
|
|
(45, 30, 272),
|
|
(41, 77, 138),
|
|
(21, 70, 1619),
|
|
(45, 73, 1876),
|
|
(35, 68, 1252),
|
|
(13, 96, 461),
|
|
(53, 57, 1575),
|
|
(82, 89, 409),
|
|
(28, 61, 449),
|
|
(58, 61, 78),
|
|
(27, 80, 1010),
|
|
(61, 58, 78),
|
|
(38, 36, 529),
|
|
(80, 30, 397),
|
|
(18, 59, 1352),
|
|
(62, 11, 1339),
|
|
(95, 59, 285),
|
|
(51, 98, 1160),
|
|
(6, 18, 696),
|
|
(30, 80, 397),
|
|
(69, 94, 1397),
|
|
(58, 85, 573),
|
|
(48, 99, 410),
|
|
(51, 46, 213),
|
|
(57, 71, 500),
|
|
(91, 30, 104),
|
|
(65, 7, 349),
|
|
(79, 51, 175),
|
|
(47, 26, 921),
|
|
(4, 61, 543),
|
|
(98, 73, 1749),
|
|
(74, 77, 1277),
|
|
(61, 28, 449),
|
|
(58, 8, 1131),
|
|
(61, 45, 1608),
|
|
(74, 87, 934),
|
|
(71, 29, 1788),
|
|
(30, 91, 104),
|
|
(13, 1, 1187),
|
|
(0, 26, 1993),
|
|
(82, 49, 1292),
|
|
(43, 87, 579),
|
|
(24, 45, 1720),
|
|
(20, 51, 868),
|
|
(77, 62, 907),
|
|
(82, 75, 306),
|
|
]
|
|
|
|
// Prepare graph and edge->cost map
|
|
var graph = Array<GraphNode>()
|
|
for n in nodes {
|
|
graph.append(GraphNode(i: n))
|
|
}
|
|
var map = Dictionary<Edge, Double>()
|
|
for tup in edges {
|
|
map[Edge(start: tup.0, end: tup.1)] = tup.2
|
|
graph[tup.0].adjList.append(tup.1)
|
|
}
|
|
|
|
// Find spanning tree
|
|
let treeEdges = prims(graph, { (start: Int, end: Int) in
|
|
return map[Edge(start: start, end: end)]!
|
|
})
|
|
|
|
// Compute its cost in order to check results
|
|
var cost = 0.0
|
|
for i in 1..<treeEdges.count {
|
|
if let n = treeEdges[i] { cost += map[Edge(start: n, end: i)]! }
|
|
}
|
|
check(Int(cost) == 49324)
|
|
}
|
|
}
|