ds-helpers
Version:
Adding priority queue library for NodeJs/javascript users
221 lines (208 loc) • 6.42 kB
JavaScript
class priorityQueue {
constructor(comparator) {
this.pqueue = [];
this.size = -1;
this.comparator = comparator ? comparator : (a,b)=>{ return a < b ;};
}
parent(index){
return parseInt((index - 1) / 2);
}
leftChild(index){
return parseInt((2 * index) + 1);
}
rightChild(index){
return parseInt((2 * index) + 2);
}
shiftUp(index){
while (index > 0 && this.comparator(this.pqueue[this.parent(index)], this.pqueue[index])) {
// Swap parent and current node
this.swap(this.parent(index), index);
// Update i to parent of i
index = this.parent(index);
}
}
swap(index1, index2){
let temp = this.pqueue[index1];
this.pqueue[index1] = this.pqueue[index2];
this.pqueue[index2] = temp;
}
shiftDown(index){
let maxOrMinIndex = index;
// Left Child
let l = this.leftChild(index);
if ( l <= this.size && this.comparator(this.pqueue[maxOrMinIndex], this.pqueue[l]) ) {
maxOrMinIndex = l;
}
// Right Child
let r = this.rightChild(index);
if ( r <= this.size && this.comparator(this.pqueue[maxOrMinIndex], this.pqueue[r]) ) {
maxOrMinIndex = r;
}
if (index != maxOrMinIndex) {
this.swap(index, maxOrMinIndex);
this.shiftDown(maxOrMinIndex);
}
}
insert(p){
this.size = this.size + 1;
this.pqueue[this.size] = p;
// Shift Up to maintain heap property
this.shiftUp(this.size);
}
extractElement(){
let result = this.pqueue[0];
// Replace the value at the root
// with the last leaf
this.pqueue[0] = this.pqueue[this.size];
this.size = this.size - 1;
// Shift down the replaced element
// to maintain the heap property
this.shiftDown(0);
return result;
}
changePriority(index, p){
let oldp = this.pqueue[index];
this.pqueue[index] = p;
if (p > oldp) {
this.shiftUp(index);
}
else {
this.shiftDown(index);
}
}
getTopElement(){
return this.pqueue[0];
}
getSize() {
return this.size+1;
}
}
/**
(function main() {
let pqueue = new priorityQueue((a,b)=>{return a.key < b.key;});
pqueue.insert({key :45 , data : null});
pqueue.insert({key :20 , data : null});
pqueue.insert({key :14 , data : null});
pqueue.insert({key :12 , data : null});
pqueue.insert({key :31 , data : null});
pqueue.insert({key :7 , data : null});
pqueue.insert({key :11 , data : null});
pqueue.insert({key :13 , data : null});
pqueue.insert({key :7 , data : null});
console.log(pqueue)
})();
*/
/*
45
/ \
31 14
/ \ / \
13 20 7 11
/ \
12 7
Create a priority queue shown in
example in a binary max heap form.
Queue will be represented in the
form of array as:
45 31 14 13 20 7 11 12 7 */
// Insert the element to the
// priority queue
module.exports = priorityQueue;
/**
function priorityQueue(pqueueType) {
this.pqueue = [];
this.size = -1;
this.pqueueType = pqueueType ? pqueueType : "max";
this.parent = (index)=>{
return parseInt((index - 1) / 2);
};
this.leftChild= (index)=> {
return parseInt((2 * index) + 1);
}
this.rightChild= (index)=> {
return parseInt((2 * index) + 2);
}
this.shiftUp= (index)=>{
if (this.pqueueType == "max") {
while (index > 0 && this.pqueue[this.parent(index)].key < this.pqueue[index].key) {
// Swap parent and current node
this.swap(this.parent(index), index);
// Update i to parent of i
index = this.parent(index);
}
} else {
while (index > 0 && this.pqueue[this.parent(index)].key > this.pqueue[index].key) {
// Swap parent and current node
this.swap(this.parent(index), index);
// Update i to parent of i
index = this.parent(index);
}
}
}
this.swap= (index1, index2)=> {
let temp = this.pqueue[index1];
this.pqueue[index1] = this.pqueue[index2];
this.pqueue[index2] = temp;
}
this.shiftDown= (index)=>{
let maxOrMinIndex = index;
if (this.pqueueType == "max") {
// Left Child
let l = this.leftChild(index);
if (l <= this.size && this.pqueue[l].key > this.pqueue[maxOrMinIndex].key) {
maxOrMinIndex = l;
}
// Right Child
let r = this.rightChild(index);
if (r <= this.size && this.pqueue[r].key > this.pqueue[maxOrMinIndex].key) {
maxOrMinIndex = r;
}
} else {
// Left Child
let l = this.leftChild(index);
if (l <= this.size && this.pqueue[l].key < this.pqueue[maxOrMinIndex].key) {
maxOrMinIndex = l;
}
// Right Child
let r = this.rightChild(index);
if (r <= this.size && this.pqueue[r].key < this.pqueue[maxOrMinIndex].key) {
maxOrMinIndex = r;
}
}
if (index != maxOrMinIndex) {
this.swap(index, maxOrMinIndex);
this.shiftDown(maxOrMinIndex);
}
}
this.insert = (p)=>{
this.size = this.size + 1;
this.pqueue[this.size] = p;
// Shift Up to maintain heap property
this.shiftUp(this.size);
}
this.extractElement = ()=>{
let result = this.pqueue[0];
// Replace the value at the root
// with the last leaf
this.pqueue[0] = this.pqueue[this.size];
this.size = this.size - 1;
// Shift down the replaced element
// to maintain the heap property
this.shiftDown(0);
return result;
}
this.changePriority = (index, p)=>{
let oldp = this.pqueue[index];
this.pqueue[index] = p;
if (p > oldp) {
this.shiftUp(index);
}
else {
this.shiftDown(index);
}
}
this.getTopElement = ()=>{
return this.pqueue[0];
}
}
*/