一日一码06——堆排序

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这个堆排序算法，采用的是最大堆；最小堆，通常在构造最小优先队列时使用。

//堆排序2013/09/29#include <stdio.h>#include <stdlib.h>#include <time.h>#include <malloc.h>int heapSize = 0;void swap(int *a, int *b){int tmp = *a;*a = *b;*b = tmp;}int left(int p){return 2*p+1; //下标从0开始的写法，如果从1开始，左子节点为2*p}int right(int p){return 2*p + 2;}int parent(int n){return (n - 1)/2;}void maxHeapify(int *a, int i){int l,r,largest;l = left(i);r = right(i);if ( l < heapSize && a[l] > a[i]) //不要写成l <= heapSize，会导致排序出错{largest = l;}else{largest = i;}if ( r < heapSize && a[r] > a[largest]){largest = r;}if (largest != i){swap(&a[largest],&a[i]);maxHeapify(a,largest);}}void buildMaxHeap(int *a){int i;for (i = (heapSize - 1) / 2; i >= 0 ; --i)     //关键点，避免了对叶子节点进行maxHeapify操作{maxHeapify(a,i);}}void heapSort(int *a){int i;for (i = heapSize - 1; i > 0; --i){swap(&a[i],&a[0]);heapSize--;//千万不要漏了maxHeapify(a,0);}}int initArr(int** a){int i,n;srand(time(NULL));printf("Input the size of array:");scanf("%d",&n);*a = (int *)malloc(n*sizeof(int));for(i = 0; i < n; i++){(*a)[i] = rand()%100; }return n;}void printArr(int* a, int n){int i;for (i = 0;i < n; i++){printf("%d,",a[i]);}printf("\n");}void main(){int* arr;int n;n = initArr(&arr);heapSize = n;printArr(arr,n);// maxHeapify(arr,0);buildMaxHeap(arr);heapSort(arr);printArr(arr,n);//printf("%d\n",0/2 );}