#include<stdio.h>
int main (void)
{
int year, month, day, sum,leap;
scanf("%d %d %d\n",&year,&month,&day);
switch(month)
{
    case1:
     sum=0;
    break;
    case2:
    sum=31;
    break;
    case3:
    sum=59;
    break;
    case4:
    sum=90;
    break;
    case5:
    sum=120;
    break;
    case6:
    sum=151;
    break;
    case7:
    sum=181;
    break;
    case8:
    sum=212;
    break;
    case9:
    sum=243;
    break;
    case10:
    sum=273;
    break;
    case11:
    sum=304;
    break;
    case12:
    sum=334;
    break;
}
sum=sum+day;
if(year%4==0)
leap=1;
else
leap=0;
if(leap==1&&month>2)
sum=sum++;
printf("%d\n",sum);
return 0;
}
 
为何运行结果是一串很长的数字？

scanf("%d %d %d\n",&year,&month,&day);
  ↓
scanf("%d %d %d",&year,&month,&day);


switch(month)
  ↓
sum = 0;
switch(month)


case1:
  ↓
case 1:

case2:
  ↓
case 2:
   .
   .
   .

sum没有赋值吧，sum=0;
不过如楼上斑斑说的scanf加\n不合适

因为你的sum没有赋初值啊，给的都是系统一个奇怪数字

#include<stdio.h>
int main (void)
{
    int year, month, day, sum=0,leap;  // 赋初始值 sum
    scanf("%d %d %d\n",&year,&month,&day);
    switch(month)
    {
case1:
        sum=0;
        break;
case2:
        sum=31;
        break;
case3:
        sum=59;
        break;
case4:
        sum=90;
        break;
case5:
        sum=120;
        break;
case6:
        sum=151;
        break;
case7:
        sum=181;
        break;
case8:
        sum=212;
        break;
case9:
        sum=243;
        break;
case10:
        sum=273;
        break;
case11:
        sum=304;
        break;
case12:
        sum=334;
        break;
    }
    sum=sum+day;
    if(year%4==0)
        leap=1;
    else
        leap=0;
    if(leap==1&&month>2)
        sum=sum++;
    printf("%d\n",sum);
    return 0;
}

1.上面是可以用的代码  环境是 vs 2010 旗舰版   debug 模式   sum 赋值就可以啦
2.如果用 vc6.0 的话，则貌似不用赋值sum 就可以  （没有亲测）  编译器不同，，要求不同，最好还是建议赋初始值

知道了  感谢