#include <stdio.h>
int add(int a, int b)
{return a + b;
}
int sub(int a, int b)
{return a - b;
}
int mul(int a, int b)
{return a * b;
}
int div(int a, int b)
{return a / b;
}
int main()
{int x, y;int input = 1;int ret = 0;do{printf("*********************\n");printf("*  1: add   2: sub  *\n");printf("*  3: mul   4: div  *\n");printf("*********************\n");printf("请选择：");scanf("%d", &input);switch (input){case 1:printf("输入操作数：");scanf("%d %d", &x, &y);ret = add(x, y);printf("ret = %d\n", ret);break;case 2:printf("输入操作数：");scanf("%d %d", &x, &y);ret = sub(x, y);printf("ret = %d\n", ret);break;case 3:printf("输入操作数：");scanf("%d %d", &x, &y);ret = mul(x, y);printf("ret = %d\n", ret);break;case 4:printf("输入操作数：");scanf("%d %d", &x, &y);ret = div(x, y);printf("ret = %d\n", ret);break;case 0:printf("退出程序\n");break;default:printf("选择错误\n");break;}} while (input);return 0;
}

#include <stdio.h>
#include <stdlib.h>
//qosrt函数的使⽤者要写一个⽐较函数
int int_cmp(const void* p1, const void* p2)
{return (*(int*)p1 - *(int*)p2);
}
int main()
{int arr[] = { 1, 3, 5, 7, 9, 2, 4, 6, 8, 0 };int i = 0;qsort(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;
}

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
struct Stu //学⽣
{char name[20];//名字int age;//年龄
};
//打印结构体
void printstruct(struct Stu* s, size_t sz)
{for (int i = 0; i < sz; i++){printf("%s %d  ", s[i].name, s[i].age);if (i == sz - 1){printf("\n");}}
}
//假设按照年龄来比较
int cmp_stu_by_age(const void* e1, const void* e2)
{return ((struct Stu*)e1)->age - ((struct Stu*)e2)->age;
}
//strcmp - 是库函数，是专门用来比较两个字符串的大小的
//假设按照名字来比较
int cmp_stu_by_name(const void* e1, const void* e2)
{return strcmp(((struct Stu*)e1)->name, ((struct Stu*)e2)->name);
}
//按照年龄来排序
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);printstruct(&s, sz);
}
//按照名字来排序
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);printstruct(&s, sz);
}
int main()
{test2();test3();return 0;
}

#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;
}

#include <stdio.h>
int main()
{int a = 10;printf("sizeof(a)   = %d\n", sizeof(a));printf("sizeof a    = %d\n", sizeof a);printf("sizeof(int) = %d\n", sizeof(int));return 0;
}

#include <stdio.h>
#include <string.h>
int main()
{char arr1[3] = { 'a', 'b', 'c' };char arr2[] = "abc";printf("strlen(arr1) = %d\n", strlen(arr1));printf("strlen(arr2) = %d\n", strlen(arr2));printf("sizeof(arr1) = %d\n", sizeof(arr1));printf("sizeof(arr2) = %d\n", sizeof(arr2));return 0;
}