下面是几种算法的C++代码实现与对比:
#include <cstdio> #include <algorithm> #include <ctime> using namespace std; //------------------------快速排序---------------------------- void quick_sort(int s[], int l, int r) { if (l < r) { int i = l, j = r, x = s[l]; while (i < j) { while(i < j && s[j] >= x) // 从右向左找第一个小于x的数 j--; if(i < j) s[i++] = s[j]; while(i < j && s[i] < x) // 从左向右找第一个大于等于x的数 i++; if(i < j) s[j--] = s[i]; } s[i] = x; quick_sort(s, l, i - 1); // 递归调用 quick_sort(s, i + 1, r); } } //------------------------归并排序---------------------------- //将有二个有序数列a[first...mid]和a[mid...last]合并。 void mergearray(int a[], int first, int mid, int last, int temp[]) { int i = first, j = mid + 1; int m = mid, n = last; int k = 0; while (i <= m && j <= n) { if (a[i] < a[j]) temp[k++] = a[i++]; else temp[k++] = a[j++]; } while (i <= m) temp[k++] = a[i++]; while (j <= n) temp[k++] = a[j++]; for (i = 0; i < k; i++) a[first + i] = temp[i]; } void mergesort(int a[], int first, int last, int temp[]) { if (first < last) { int mid = (first + last) / 2; mergesort(a, first, mid, temp); //左边有序 mergesort(a, mid + 1, last, temp); //右边有序 mergearray(a, first, mid, last, temp); //再将二个有序数列合并 } } bool MergeSort(int a[], int n) { int *p = new int[n]; if (p == NULL) return false; mergesort(a, 0, n - 1, p); return true; } //------------------------堆排序--------------------------- inline void Swap(int &a, int &b) { int c = a; a = b; b = c; } //建立最小堆 // 从i节点开始调整,n为节点总数 从0开始计算 i节点的子节点为 2*i+1, 2*i+2 void MinHeapFixdown(int a[], int i, int n) { int j, temp; temp = a[i]; j = 2 * i + 1; while (j < n) { if (j + 1 < n && a[j + 1] < a[j]) //在左右孩子中找最小的 j++; if (a[j] >= temp) break; a[i] = a[j]; //把较小的子结点往上移动,替换它的父结点 i = j; j = 2 * i + 1; } a[i] = temp; } //建立最小堆 void MakeMinHeap(int a[], int n) { for (int i = n / 2 - 1; i >= 0; i--) MinHeapFixdown(a, i, n); } void MinheapsortTodescendarray(int a[], int n) { for (int i = n - 1; i >= 1; i--) { Swap(a[i], a[0]); MinHeapFixdown(a, 0, i); } } const int MAXN = 5000000; int a[MAXN]; int b[MAXN], c[MAXN], d[MAXN]; int main() { int i; srand(time(NULL)); for (i = 0; i < MAXN; ++i) a[i] = rand() * rand(); //注rand()产生的数在0到0x7FFF之间 for (i = 0; i < MAXN; ++i) d[i] = c[i] = b[i] = a[i]; clock_t ibegin, iend; printf("--当前数据量为%d\n", MAXN); //快速排序 printf("快速排序: "); ibegin = clock(); quick_sort(a, 0, MAXN - 1); iend = clock(); printf("%d毫秒\n", iend - ibegin); //归并排序 printf("归并排序: "); ibegin = clock(); MergeSort(b, MAXN); iend = clock(); printf("%d毫秒\n", iend - ibegin); //堆排序 printf("堆排序: "); ibegin = clock(); MakeMinHeap(c, MAXN); MinheapsortTodescendarray(c, MAXN); iend = clock(); printf("%d毫秒\n", iend - ibegin); //STL中的堆排序 printf("STL中的堆排序: "); ibegin = clock(); make_heap(d, d + MAXN); sort_heap(d, d + MAXN); iend = clock(); printf("%d毫秒\n", iend - ibegin); return 0; }