Introduction To Algorithms-HeapSort-BuildHeap

// maxHeap.cpp : Defines the entry point for the console application.//#include "stdafx.h"#define LENGTH(x) (sizeof(x)/sizeof(x[0]))static int heap_size = 0;int parent(int i){return (i)/2;}int left(int i){return 2*(i);}int right(int i){return 2*(i)+1;}void maxHeapify(int A[], int i){int largest;int l, r, tmpdata;l = left(i);r = right(i);if (l < heap_size && A[l] > A[i]) largest = l;else largest = i;if (r < heap_size && A[r] > A[largest])largest = r;if (largest != i) {tmpdata = A[i];A[i] = A[largest];A[largest] = tmpdata;maxHeapify(A, largest);}}void buildMaxHeap(int A[], int len){int i;heap_size = len;for (i = (len)/2; i > 0; i--)maxHeapify(A, i);}inline void dumpHeap(int A[], int len){int i;for (i = 0; i < len; i++)printf("%4d", A[i]);printf("/n");}int main(int argc, char* argv[]){int A[] = {0, 4, 1, 3, 2, 16, 9, 10, 14, 8, 7};printf("heap size:%d/n", LENGTH(A));dumpHeap(A, LENGTH(A));buildMaxHeap(A, LENGTH(A));dumpHeap(A, LENGTH(A));return 0;} 

下标为largest的节点在交换后的值为A[i],以该节点为根的子树又有可能违反最大堆的性质，因而要递归子树调用maxHeapify.