一、定義

二、用qsort函數排序整型數據

#include<stdio.h>
scanf_S(int *arr,int sz)
{for (int i = 0; i < sz; i++){scanf("%d", &arr[i]);}
}
int int_cmp(const void*p1,const void*p2)
{return(*(int*)p1 - *(int*)p2);
}                           
print(int *arr,int sz)
{for (int i = 0; i < sz; i++){printf("%d ", arr[i]);}
}int main()
{int arr[10] = { 0 };int sz = sizeof(arr) / sizeof(arr[0]);scanf_S(arr,sz);qsort(arr, sz, sizeof(int), int_cmp);                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 print(arr, sz);return 0;
}

三、用qsort排序結構數據

部分代碼

struct Stu //學?
{char name[20];//名字int age;//年齡
};
//假設按照年齡來?較
int cmp_stu_by_age(const void* e1, const void* e2)
{return ((struct Stu*)e1)->age - ((struct Stu*)e2)->age;
}
//strcmp - 是庫函數，是專??來?較兩個字符串的??的
//假設按照名字來?較
int cmp_stu_by_name(const void* e1, const void* e2)
{return strcmp(((struct Stu*)e1)->name, ((struct Stu*)e2)->name);
}
//按照年齡來排序
void test2()
{struct Stu s[] = { {"zhangsan", 20}, {"lisi", 30}, {"wangwu", 15} };int sz = sizeof(s) / sizeof(s[0]);qsort(s, sz, sizeof(s[0]), cmp_stu_by_age);
}
void test3()
{struct Stu s[] = { {"zhangsan", 20}, {"lisi", 30}, {"wangwu", 15} };int sz = sizeof(s) / sizeof(s[0]);qsort(s, sz, sizeof(s[0]), cmp_stu_by_name);
}
int main()
{test2();test3();return 0;
}

四、qsort函數的模擬實現

使用回調函數，模擬實現qsort（采用冒泡的方式）。

#include <stdio.h>int int_cmp(const void* p1, const void* p2)
{return (*(int*)p1 - *(int*)p2);
}
void _swap(void* p1, void* p2, int size)
{int i = 0;for (i = 0; i < size; i++){char tmp = *((char*)p1 + i);*((char*)p1 + i) = *((char*)p2 + i);*((char*)p2 + i) = tmp;}
}
void bubble(void* base, int count, int size, int(*cmp)(void*, void*))
{int i = 0;int j = 0;for (i = 0; i < count - 1; i++){for (j = 0; j < count - i - 1; j++){if (cmp((char*)base + j * size, (char*)base + (j + 1) * size) > 0){_swap((char*)base + j * size, (char*)base + (j + 1) * size, size);}}}
}
int main()
{int arr[] = { 1, 3, 5, 7, 9, 2, 4, 6, 8, 0 };int i = 0;bubble(arr, sizeof(arr) / sizeof(arr[0]), sizeof(int), int_cmp);for (i = 0; i < sizeof(arr) / sizeof(arr[0]); i++){printf("%d ", arr[i]);}printf("\n");return 0;
}

歐耶！！！我學會啦！！！！