fix: use KeyPriorityQueue in PrimMST TheAlgorithms#1298

Author: paulinegarelli

Graphs/PrimMST.js

@@ -1,148 +1,4 @@
-// Priority Queue Helper functions
-function getParentPosition (position) {
-  // Get the parent node of the current node
-  return Math.floor((position - 1) / 2)
-}
-function getChildrenPosition (position) {
-  // Get the children nodes of the current node
-  return [2 * position + 1, 2 * position + 2]
-}
-
-class PriorityQueue {
-  // Priority Queue class using Minimum Binary Heap
-  constructor () {
-    this._heap = []
-    this.keys = {}
-  }
-
-  isEmpty () {
-    // Checking if the heap is empty
-    return this._heap.length === 0
-  }
-
-  push (key, priority) {
-    // Adding element to the queue (equivalent to add)
-    this._heap.push([key, priority])
-    this.keys[key] = this._heap.length - 1
-    this._shiftUp(this.keys[key])
-  }
-
-  pop () {
-    // Removing the element with least priority (equivalent to extractMin)
-    this._swap(0, this._heap.length - 1)
-    const [key] = this._heap.pop()
-    delete this.keys[key]
-    this._shiftDown(0)
-    return key
-  }
-
-  contains (key) {
-    // Check if a given key is present in the queue
-    return (key in this.keys)
-  }
-
-  update (key, priority) {
-    // Update the priority of the given element (equivalent to decreaseKey)
-    const currPos = this.keys[key]
-    this._heap[currPos][1] = priority
-    const parentPos = getParentPosition(currPos)
-    const currPriority = this._heap[currPos][1]
-    let parentPriority = Infinity
-    if (parentPos >= 0) {
-      parentPriority = this._heap[parentPos][1]
-    }
-    const [child1Pos, child2Pos] = getChildrenPosition(currPos)
-    let [child1Priority, child2Priority] = [Infinity, Infinity]
-    if (child1Pos < this._heap.length) {
-      child1Priority = this._heap[child1Pos][1]
-    }
-    if (child2Pos < this._heap.length) {
-      child2Priority = this._heap[child2Pos][1]
-    }
-
-    if (parentPos >= 0 && parentPriority > currPriority) {
-      this._shiftUp(currPos)
-    } else if (child2Pos < this._heap.length &&
-      (child1Priority < currPriority || child2Priority < currPriority)) {
-      this._shiftDown(currPos)
-    }
-  }
-
-  _shiftUp (position) {
-    // Helper function to shift up a node to proper position (equivalent to bubbleUp)
-    let currPos = position
-    let parentPos = getParentPosition(currPos)
-    let currPriority = this._heap[currPos][1]
-    let parentPriority = Infinity
-    if (parentPos >= 0) {
-      parentPriority = this._heap[parentPos][1]
-    }
-
-    while (parentPos >= 0 && parentPriority > currPriority) {
-      this._swap(currPos, parentPos)
-      currPos = parentPos
-      parentPos = getParentPosition(currPos)
-      currPriority = this._heap[currPos][1]
-      try {
-        parentPriority = this._heap[parentPos][1]
-      } catch (error) {
-        parentPriority = Infinity
-      }
-    }
-    this.keys[this._heap[currPos][0]] = currPos
-  }
-
-  _shiftDown (position) {
-    // Helper function to shift down a node to proper position (equivalent to bubbleDown)
-    let currPos = position
-    let [child1Pos, child2Pos] = getChildrenPosition(currPos)
-    let [child1Priority, child2Priority] = [Infinity, Infinity]
-    if (child1Pos < this._heap.length) {
-      child1Priority = this._heap[child1Pos][1]
-    }
-    if (child2Pos < this._heap.length) {
-      child2Priority = this._heap[child2Pos][1]
-    }
-    let currPriority
-    try {
-      currPriority = this._heap[currPos][1]
-    } catch {
-      return
-    }
-
-    while (child2Pos < this._heap.length &&
-      (child1Priority < currPriority || child2Priority < currPriority)) {
-      if (child1Priority < currPriority && child1Priority < child2Priority) {
-        this._swap(child1Pos, currPos)
-        currPos = child1Pos
-      } else {
-        this._swap(child2Pos, currPos)
-        currPos = child2Pos
-      }
-      [child1Pos, child2Pos] = getChildrenPosition(currPos)
-      try {
-        [child1Priority, child2Priority] = [this._heap[child1Pos][1], this._heap[child2Pos][1]]
-      } catch (error) {
-        [child1Priority, child2Priority] = [Infinity, Infinity]
-      }
-
-      currPriority = this._heap[currPos][1]
-    }
-    this.keys[this._heap[currPos][0]] = currPos
-    if (child1Pos < this._heap.length && child1Priority < currPriority) {
-      this._swap(child1Pos, currPos)
-      this.keys[this._heap[child1Pos][0]] = child1Pos
-    }
-  }
-
-  _swap (position1, position2) {
-    // Helper function to swap 2 nodes
-    [this._heap[position1], this._heap[position2]] = [this._heap[position2], this._heap[position1]]
-    this.keys[this._heap[position1][0]] = position1
-    this.keys[this._heap[position2][0]] = position2
-  }
-}
-
+import { KeyPriorityQueue } from "../Data-Structures/Heap/KeyPriorityQueue"
 class GraphWeightedUndirectedAdjacencyList {
   // Weighted Undirected Graph class
   constructor () {
@@ -167,7 +23,7 @@ class GraphWeightedUndirectedAdjacencyList {
     // Details: https://en.wikipedia.org/wiki/Prim%27s_algorithm
     const distance = {}
     const parent = {}
-    const priorityQueue = new PriorityQueue()
+    const priorityQueue = new KeyPriorityQueue()
     // Initialization
     for (const node in this.connections) {
       distance[node] = (node === start.toString() ? 0 : Infinity)
@@ -198,11 +54,3 @@ class GraphWeightedUndirectedAdjacencyList {
 }
 
 export { GraphWeightedUndirectedAdjacencyList }
-
-// const graph = new GraphWeightedUndirectedAdjacencyList()
-// graph.addEdge(1, 2, 1)
-// graph.addEdge(2, 3, 2)
-// graph.addEdge(3, 4, 1)
-// graph.addEdge(3, 5, 100) // Removed in MST
-// graph.addEdge(4, 5, 5)
-// graph.PrimMST(1)