题目：输入某年某月某日，判断这一天是这一年的第几天？

代码如下：

#include <stdio.h>

/**
 *  输入某年某月某日，判断这一天是这一年的第几天？
 *  create by hangli
 */
int main(int argc, char *argv[])

{

    int y, m, d, days, February;

    printf("请输入年份:");

    scanf("%d", &y);

    printf("请输入月份:");

    scanf("%d", &m);

    printf("请输入天:");

    scanf("%d", &d);

    // 先判断是是否是闰年
    if (y % 400 == 0 || (y % 4 == 0 && y % 100 != 0))

        February = 29;

    else

        February = 28;

    switch (m)
    {
    // 分别计算每个月的天数
    case 1:

        days = 0;

        printf("%d年%d月%d日是一年中的第%d天！", y, m, d, days + d);

        break;

    case 2:

        days = 31;

        printf("%d年%d月%d日是一年中的第%d天！", y, m, d, days + d);

        break;

    case 3:

        days = 31 + February;

        printf("%d年%d月%d日是一年中的第%d天！", y, m, d, days + d);

        break;

    case 4:

        days = 62 + February;

        printf("%d年%d月%d日是一年中的第%d天！", y, m, d, days + d);

        break;

    case 5:

        days = 92 + February;

        printf("%d年%d月%d日是一年中的第%d天！", y, m, d, days + d);

        break;

    case 6:

        days = 123 + February;

        printf("%d年%d月%d日是一年中的第%d天！", y, m, d, days + d);

        break;

    case 7:

        days = 153 + February;

        printf("%d年%d月%d日是一年中的第%d天！", y, m, d, days + d);

        break;

    case 8:

        days = 184 + February;

        printf("%d年%d月%d日是一年中的第%d天！", y, m, d, days + d);

        break;

    case 9:

        days = 215 + February;

        printf("%d年%d月%d日是一年中的第%d天！", y, m, d, days + d);

        break;

    case 10:

        days = 245 + February;

        printf("%d年%d月%d日是一年中的第%d天！", y, m, d, days + d);

        break;

    case 11:

        days = 276 + February;

        printf("%d年%d月%d日是一年中的第%d天！", y, m, d, days + d);

        break;

    case 12:

        days = 306 + February;

        printf("%d年%d月%d日是一年中的第%d天！", y, m, d, days + d);

        break;

    default:

        printf("你输入月份错误!");

        break;
    }

    system("PAUSE");

    return 0;
}

运行结果截图