第7章 快速排序
7.1 快速排序的描述
#include <stdio.h>#include <time.h>#include <stdlib.h>#include <string.h>void swap(void *a, void *b, size_t elem_size){if(a==NULL||b==NULL||a==b)return;char temp[elem_size];/*变长数组 */memcpy(temp, a, elem_size);memcpy(a, b, elem_size);memcpy(b, temp, elem_size);}int partition(void *base, size_t elem_size, int p, int r, int (*comp) (const void *, const void *)){char *cbase = base;void *key = &cbase[r * elem_size];int i = p - 1;for (int j = p; j < r; j++) {if (comp(&cbase[j * elem_size], key) <= 0) {++i;swap(&cbase[i * elem_size], &cbase[j * elem_size], elem_size);}}swap(&cbase[(i + 1) * elem_size], key, elem_size);return i + 1;}void quick_sort(void *base, size_t elem_size, int p, int r, int (*comp) (const void *, const void *)){if (p < r) {int q = partition(base, elem_size, p, r, comp);quick_sort(base, elem_size, p, q - 1, comp);quick_sort(base, elem_size, q + 1, r, comp);}}void randomized_in_place(void *array, size_t elem_size, int length){char *carray = array;for (int i = 0; i < length; i++) {int rand_index = rand() % (length - i) + i;swap(&carray[i * elem_size], &carray[rand_index * elem_size], elem_size);}}void print_array(int a[], int length){for (int i = 0; i < length; i++) {printf("%d ", a[i]);}printf("\n");}int cmp_int(const void *p1, const void *p2){const int *pa = p1;const int *pb = p2;if (*pa < *pb)return -1;if (*pa == *pb)return 0;return 1;}int main(void){srand((unsigned)time(NULL));int a[10];for (int i = 0; i < 10; i++) {a[i] = i;}randomized_in_place(a, sizeof(int), 10);printf("排序前:\n");print_array(a, 10);quick_sort(a, sizeof(int), 0, 9, cmp_int);printf("排序后:\n");print_array(a, 10);return 0;}7.3 快速排序的随机化版本
#include <stdio.h>#include <time.h>#include <stdlib.h>#include <string.h>void swap(void *a, void *b, size_t elem_size){if(a==NULL||b==NULL||a==b)return;char temp[elem_size];/*变长数组 */memcpy(temp, a, elem_size);memcpy(a, b, elem_size);memcpy(b, temp, elem_size);}int partition(void *base, size_t elem_size, int p, int r, int (*comp) (const void *, const void *)){char *cbase = base;void *key = &cbase[r * elem_size];int i = p - 1;for (int j = p; j < r; j++) {if (comp(&cbase[j * elem_size], key) <= 0) {++i;swap(&cbase[i * elem_size], &cbase[j * elem_size], elem_size);}}swap(&cbase[(i + 1) * elem_size], key, elem_size);return i + 1;}int randomized_partition(void *base, size_t elem_size, int p, int r,int (*comp) (const void *, const void *)){char *cbase = base;int i = rand() % (r - p + 1) + p;swap(&cbase[r * elem_size], &cbase[i * elem_size], elem_size);return partition(base, elem_size, p, r, comp);}void randomize_quick_sort(void *base, size_t elem_size, int p, int r,int (*comp) (const void *, const void *)){if (p < r) {int q = randomized_partition(base, elem_size, p, r, comp);randomize_quick_sort(base, elem_size, p, q - 1, comp);randomize_quick_sort(base, elem_size, q + 1, r, comp);}}void randomized_in_place(void *array, size_t elem_size, int length){char *carray = array;for (int i = 0; i < length; i++) {int n_rand_index = rand() % (length - i) + i;swap(&carray[i * elem_size], &carray[n_rand_index * elem_size], elem_size);}}void print_array(int a[], int length){for (int i = 0; i < length; i++) {printf("%d ", a[i]);}printf("\n");}int cmp_int(const void *p1, const void *p2){const int *pa = p1;const int *pb = p2;if (*pa < *pb)return -1;if (*pa == *pb)return 0;return 1;}int main(void){srand((unsigned)time(NULL));int a[10];for (int i = 0; i < 10; i++) {a[i] = i;}randomized_in_place(a, sizeof(int), 10);printf("排序前:\n");print_array(a, 10);randomize_quick_sort(a, sizeof(int), 0, 9, cmp_int);printf("排序后:\n");print_array(a, 10);return 0;}
