Max heap implementation (TheAlgorithms#157)

samjain2907 · web-flow · commit 728363024a26 · 2020-05-08T04:21:27.000+05:30
* Added MaxHeap implementation

* Added MaxHeap implementation

* Added MaxHeap implementation

* Added MaxHeap implementation

* Delete package-lock.json

* Delete .gitignore
diff --git a/Data-Structures/Heap/MaxHeap.js b/Data-Structures/Heap/MaxHeap.js
@@ -0,0 +1,85 @@
+/**
+ * Author: Samarth Jain
+ * Max Heap implementation in Javascript
+ */
+
+class BinaryHeap {
+  constructor () {
+    this.heap = []
+  }
+
+  insert (value) {
+    this.heap.push(value)
+    this.heapify()
+  }
+
+  size () {
+    return this.heap.length
+  }
+
+  empty () {
+    return this.size() === 0
+  }
+
+  // using iterative approach to reorder the heap after insertion
+  heapify () {
+    let index = this.size() - 1
+
+    while (index > 0) {
+      const element = this.heap[index]
+      const parentIndex = Math.floor((index - 1) / 2)
+      const parent = this.heap[parentIndex]
+
+      if (parent[0] >= element[0]) break
+      this.heap[index] = parent
+      this.heap[parentIndex] = element
+      index = parentIndex
+    }
+  }
+
+  // Extracting the maximum element from the Heap
+  extractMax () {
+    const max = this.heap[0]
+    const tmp = this.heap.pop()
+    if (!this.empty()) {
+      this.heap[0] = tmp
+      this.sinkDown(0)
+    }
+    return max
+  }
+
+  // To restore the balance of the heap after extraction.
+  sinkDown (index) {
+    const left = 2 * index + 1
+    const right = 2 * index + 2
+    let largest = index
+    const length = this.size()
+
+    if (left < length && this.heap[left][0] > this.heap[largest][0]) {
+      largest = left
+    }
+    if (right < length && this.heap[right][0] > this.heap[largest][0]) {
+      largest = right
+    }
+    // swap
+    if (largest !== index) {
+      const tmp = this.heap[largest]
+      this.heap[largest] = this.heap[index]
+      this.heap[index] = tmp
+      this.sinkDown(largest)
+    }
+  }
+}
+
+const maxHeap = new BinaryHeap()
+maxHeap.insert([4])
+maxHeap.insert([3])
+maxHeap.insert([6])
+maxHeap.insert([1])
+maxHeap.insert([8])
+maxHeap.insert([2])
+
+while (!maxHeap.empty()) {
+  const mx = maxHeap.extractMax()
+  console.log(mx)
+}
