#include<stdio.h>
#include<stdlib.h>
int main()
{
    long int gain;
    int prize1,prize2,prize4,prize6,prize10,prize=0.0;
    printf("***********************************************\n");
    printf("*     The program will solve                  *\n");
    printf("    the problem of prize distribution         *\n");
    printf("***********************************************\n");
    printf("please input the num of gain:");
    scanf("%ld",&gain);
    prize1=100000*0.1;
    prize2=prize1+100000*0.075;
    prize4=prize2+200000*0.05;
    prize6=prize4+200000*0.03;
    prize10=prize6+400000*0.015;
    if(gain<=100000)
        prize=gain*0.1;
    else if(gain<=200000)
        prize=prize1+(gain-100000)*0.075;
    else if(gain<=400000)
        prize=prize2+(gain-200000)*0.05;
    else if(gain<=600000)
        prize=prize4+(gain-400000)*0.03;
    else if(gain<=1000000)
        prize=prize6+(gain-600000)*0.015;
    else
        prize=prize10+(gain-1000000)*0.01;
    printf("The prize is:%d\n",prize);
    return 0;
}将第六行int 改为double后结果出现错误，不管输入任何数，结果都为0！

坐等围观。。。。。。。

既然该了 int为 double 输出 %d 就不对

你定义了double prize=0.0;
输出用:%d\n",prize
能对吗

好多啊、、 晕啊、、

你现在的这个程序有问题吧
你将int改为double型后
后面的输出语句也要跟着改成printf("The prize is:%lf\n",prize);

同意楼上！C语言对整数类型的要求特别严！
要注意整数类型的转换！