#include "stdio.h"
#include "string.h"
int main()
{
    int i,js=0,ro=0,key;
    char str[16];
    printf("输入信用卡号:");
    gets(str);
    if(strlen(str)<16)
    {
        printf("失败");
        
    }
    for(i=strlen(str)-1;i<16;i--)
    {
        if(i%2!=0)
        {
        js+=str[i]-'0';   
        }
            else
            {
        if((str[i]-'0')*2>=10)
        ro+=(str[i]-'0')*2-9;
        else ro+=str[i]-'0';   
            }
    }
    key=js+ro;
    if(key%10==0)
    {
        printf("成功");
        printf("%s\n",str);
    }
    else printf("失败");
    return 0;
}
-------------------------------
编译结果...
--------
- 错误: 0
- 警告: 0
- 输出文件名: D:\myc\信用卡.exe
- 输出大小: 128.26953125 KiB
- 编译时间: 0.61s