Merge pull request #387 from ahmibr/heap_sort

Add heap sort

Author: probot-auto-merge[bot]

Searching and Sorting/Heap Sort/HeapSort.cpp

@@ -0,0 +1,53 @@
+#include "HeapSort.h"
+#include <algorithm>
+
+HeapSort::HeapSort() {
+	heapSize = 0;
+}
+
+HeapSort::~HeapSort() {};
+void HeapSort::sort(int* arr, int size) {
+
+	buildMaxHeap(arr, size);
+	for (int i = size - 1; i > 0; --i) {
+		//arr[0] is the largest element in heap, put it in the end
+		std::swap(arr[0], arr[i]);
+
+		//heap size is decreased after removing an element
+		--heapSize;
+
+		//heap is corrupted now, fix it
+		maxHeapify(arr, 0);
+	}
+
+}
+
+void HeapSort::maxHeapify(int* arr, int idx) {
+
+	while (1) {
+		int left = LEFT(idx);
+		int right = RIGHT(idx);
+
+		int largestIdx = idx;
+
+		//get max element from me,my left child, my right child
+		if (left < heapSize && arr[left] > arr[largestIdx])
+			largestIdx = left;
+
+		if (right < heapSize && arr[right] > arr[largestIdx])
+			largestIdx = right;
+
+		if (largestIdx == idx) //now it remains heap property
+			break;
+
+		//arr[largestIdx] now contains the smaller element to be pushed down
+		std::swap(arr[idx], arr[largestIdx]);
+		idx = largestIdx;
+	}
+}
+
+void HeapSort::buildMaxHeap(int* arr, int size) {
+	heapSize = size;
+	for (int i = ((size) >> 1) - 1; i >= 0; --i)
+		maxHeapify(arr, i);
+}

Searching and Sorting/Heap Sort/HeapSort.h

@@ -0,0 +1,21 @@
+#ifndef HEAPSORT_HEAPSORT_H_
+#define HEAPSORT_HEAPSORT_H_
+
+//Helper macros to access left,right child and parent
+#define RIGHT(i) ((i<<1)+2) 
+#define LEFT(i) ((i<<1)+1)
+#define PARENT(i) ((i-1)>>1)
+
+class HeapSort:{
+
+private:
+	int heapSize;
+	void maxHeapify(int* arr, int idx);
+	void buildMaxHeap(int* arr, int size);
+public:
+	HeapSort();
+	virtual void sort(int* arr, int size);
+	virtual ~HeapSort();
+};
+
+#endif /* HEAPSORT_HEAPSORT_H_ */