update: added MaxHeap

Author: ashokdey

src/_DataStructures_/Heaps/MaxHeap/index.js

@@ -0,0 +1,74 @@
+class MaxHeap {
+  constructor() {
+    this.heap = [];
+  }
+
+  add(element) {
+    this.heap.push(element);
+    // check for the parent element & swap if required
+    // eslint-disable-next-line no-underscore-dangle
+    this.__traverseUpAndSwap(this.heap.length - 1);
+  }
+
+  getMax() {
+    return this.heap[0] || null;
+  }
+
+  remove() {
+    // return the element at the root
+    const max = this.heap[0] || null;
+    if (this.heap.length > 1) {
+      // move the leaf to the root
+      this.heap[0] = this.heap[this.heap.length - 1];
+      this.heap.splice(this.heap.length - 1, 1);
+      // restore the heapify property
+      // eslint-disable-next-line no-underscore-dangle
+      this.__heapify(0);
+      return max;
+    }
+
+    if (this.heap.length === 1) {
+      this.heap.splice(this.heap.length - 1, 1);
+      return max;
+    }
+
+    return max;
+  }
+
+  __heapify(index) {
+    const left = index * 2;
+    const right = index * 2 + 1;
+    let largest = index;
+
+    if (this.heap.length > left && this.heap[largest] < this.heap[left]) {
+      largest = left;
+    }
+
+    if (this.heap.length > right && this.heap[largest] < this.heap[right]) {
+      largest = right;
+    }
+
+    if (largest !== index) {
+      const temp = this.heap[largest];
+      this.heap[largest] = this.heap[index];
+      this.heap[index] = temp;
+      // eslint-disable-next-line no-underscore-dangle
+      this.__heapify(largest);
+    }
+  }
+
+  __traverseUpAndSwap(index) {
+    if (index <= 0) return;
+    const parent = Math.floor(index / 2);
+
+    if (this.heap[parent] < this.heap[index]) {
+      const temp = this.heap[parent];
+      this.heap[parent] = this.heap[index];
+      this.heap[index] = temp;
+      // eslint-disable-next-line no-underscore-dangle
+      this.__traverseUpAndSwap(parent);
+    }
+  }
+}
+
+module.exports = MaxHeap;