From db8369efaf40f4760c3470788bdc14d2b6266c22 Mon Sep 17 00:00:00 2001
From: Manish <manish@radii.dev>
Date: Sun, 17 Sep 2023 18:52:24 +1000
Subject: [PATCH] Data Structures: Create a Priority Queue Class

---
 Data Structures/priorityQueueClass.js | 74 +++++++++++++++++++++++++++
 1 file changed, 74 insertions(+)
 create mode 100644 Data Structures/priorityQueueClass.js

diff --git a/Data Structures/priorityQueueClass.js b/Data Structures/priorityQueueClass.js
new file mode 100644
index 0000000..6370ae4
--- /dev/null
+++ b/Data Structures/priorityQueueClass.js	
@@ -0,0 +1,74 @@
+// https://www.freecodecamp.org/learn/coding-interview-prep/data-structures/create-a-priority-queue-class
+
+function PriorityQueue() {
+  this.collection = [];
+  this.printCollection = function () {
+    console.log(
+      this.collection.map(([elem, priority, order]) => [elem, priority])
+    );
+  };
+  // Only change code below this line
+  this.order = 0;
+  this.size = function () {
+    return this.collection.length;
+  };
+  this.isEmpty = function () {
+    return !this.collection.length;
+  };
+  this.swap = function (a, b) {
+    const tmp = this.collection[a];
+    this.collection[a] = this.collection[b];
+    this.collection[b] = tmp;
+  };
+  this.changePriority = function (a, b) {
+    return (
+      this.collection[a][1] > this.collection[b][1] ||
+      (this.collection[a][1] == this.collection[b][1] &&
+        this.collection[a][2] > this.collection[b][2])
+    );
+  };
+  this.enqueue = function (elem) {
+    elem.push(this.order++);
+    this.collection.push(elem);
+    let me = this.collection.length - 1;
+    let parent = Math.trunc((me - 1) / 2);
+    while (this.changePriority(parent, me)) {
+      this.swap(parent, me);
+      me = parent;
+      parent = Math.trunc((me - 1) / 2);
+    }
+  };
+  this.dequeue = function () {
+    if (this.isEmpty()) return;
+    this.swap(0, this.collection.length - 1);
+    const elem = this.collection.pop()[0];
+    let me = 0;
+    let leftChild = me * 2 + 1;
+    let rightChild = leftChild + 1;
+    while (
+      (leftChild < this.collection.length &&
+        this.changePriority(me, leftChild)) ||
+      (rightChild < this.collection.length &&
+        this.changePriority(me, rightChild))
+    ) {
+      if (
+        rightChild < this.collection.length &&
+        this.changePriority(leftChild, rightChild)
+      ) {
+        this.swap(me, rightChild);
+        me = rightChild;
+      } else {
+        this.swap(me, leftChild);
+        me = leftChild;
+      }
+      leftChild = me * 2 + 1;
+      rightChild = leftChild + 1;
+    }
+    return elem;
+  };
+  this.front = function () {
+    if (this.isEmpty()) return;
+    return this.collection[0][0];
+  };
+  // Only change code above this line
+}