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使用main函数的参数，实现一个整数计算器

程序可以接受三个参数,第一个参数“ - a”选项执行加法，“ - s”选项执行减法，“ - m”选项执行乘法，“ - d”选项执行除法，后面两个参数为操作数。

#include<stdio.h>
#include<stdlib.h>

int main(int argc, char *argv[], char *envp[])
{
    int ret = 0;
    if (argc != 4)
        printf("参数个数错误，argc=%d\n", argc);
    else
    {
        switch (*(argv[1] + 1))
        {
        case 'a':
            ret = atoi(argv[2]) + atoi(argv[3]);
            break;
        case 's':
            ret = atoi(argv[2]) - atoi(argv[3]);
            break;
        case 'm':
            ret = atoi(argv[2]) / atoi(argv[3]);
            break;
        case 'd':
            ret = atoi(argv[2])*atoi(argv[3]);
            break;
        default:
            printf("输入有误.\n");
            break;
        }
        printf("ret=%d\n", ret);
    }
    system("pause");
    return 0;
}

冒泡排序可以排序多个字符串

#include<stdio.h>
#include<stdlib.h>
#include<assert.h>

int cmp_string(char *str1, char *str2)
{
    assert(str1&&str2);
    while (*str1 == *str2)
    {
        if (*str1 == '\0')
            return 0;
        str1++;
        str2++;
    }
    if (*str1 > *str2)
        return 1;
    else
        return -1;
}

void _Swap(char *str1, char *str2, size_t sz)
{
    assert(str1&&str2);
    unsigned int i = 0;
    for (i = 0; i < sz; i++)
    {
        char tmp = *str1;
        *str1 = *str2;
        *str2 = tmp;
        str1++;
        str2++;
    }
}


void bubble_sort(void *base, int num, int width, int(*cmp)(const void*e1, const void*e2))
{
    assert(base != NULL);
    int i = 0;
    int j = 0;
    for (i = 0; i < num - 1; i++)
    {
        for (j = 0; j < num - i - 1; j++)
        {
            if (cmp((char *)base + j*width, (char *)base + (j + 1)*width) >0 )
                _Swap(((char *)base + j*width), ((char *)base + (j + 1)*width), width);
        }
    }
}

int main()
{
    int i = 0;
    char *arr[] = { "zhangsan", "lisi", "wangwu" };
    int sz = sizeof(arr) / sizeof(arr[0]);
    bubble_sort(arr, sz, sizeof(arr[0]), cmp_string);
    for (i = 0; i < sz; i++)
        printf("%s\n", arr[i]);
    system("pause");
    return 0;
}