update: added MinHeap, support for collection in constructor

Author: ashokdey

src/_DataStructures_/Heaps/MaxHeap/index.js

@@ -1,6 +1,11 @@
 class MaxHeap {
-  constructor() {
+  constructor(collection) {
     this.heap = [];
+    if (collection) {
+      collection.forEach((element) => {
+        this.add(element);
+      });
+    }
   }
 
   add(element) {
@@ -25,13 +30,13 @@ class MaxHeap {
       // restore the heapify property
       // eslint-disable-next-line no-underscore-dangle
       this.__heapify(0);
-      return max;
     }
 
     if (this.heap.length === 1) {
       this.heap.pop();
-      return max;
     }
+
+    return max;
   }
 
   __heapify(index) {

src/_DataStructures_/Heaps/MinHeap/index.js

@@ -0,0 +1,79 @@
+class MinHeap {
+  constructor(collection) {
+    this.heap = [];
+
+    if (collection) {
+      collection.forEach((element) => {
+        this.add(element);
+      });
+    }
+  }
+
+  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);
+  }
+
+  getMin() {
+    return this.heap[0] || null;
+  }
+
+  remove() {
+    const min = this.heap[0] || null;
+
+    if (this.heap.length > 1) {
+      this.heap[0] = this.heap[this.heap.length - 1];
+      this.heap.pop();
+      // eslint-disable-next-line no-underscore-dangle
+      this.__heapify(0);
+    }
+    if (this.heap.length === 1) {
+      this.heap.pop();
+    }
+    return min;
+  }
+
+  destroy() {
+    this.heap = [];
+  }
+
+  // eslint-disable-next-line consistent-return
+  __traverseUpAndSwap(index) {
+    if (index <= 0) return null;
+
+    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);
+    }
+  }
+
+  __heapify(index) {
+    const left = index * 2;
+    const right = index * 2 + 1;
+
+    let smallest = index;
+
+    if (this.heap.length > left && this.heap[smallest] > this.heap[left]) {
+      smallest = left;
+    }
+    if (this.heap.length > right && this.heap[smallest] > this.heap[right]) {
+      smallest = right;
+    }
+    if (smallest !== index) {
+      const tmp = this.heap[smallest];
+      this.heap[smallest] = this.heap[index];
+      this.heap[index] = tmp;
+      // eslint-disable-next-line no-underscore-dangle
+      this.__heapify(smallest);
+    }
+  }
+}
+
+module.exports = MinHeap;