int y = 0, m = 0, d = 0;
    int sum = 0;//用来存储其位这一年的第几天
    printf("第七题:请输入年月日:");
    scanf("%d%d%d", &y, &m, &d);
    int a[12] = {31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
    int b[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
   
    if (y % 400 == 0 || (y % 4 ==0 && y % 100 != 0)) {
        for (int j = 0; j < m - 1; j++) {
            sum += a[j];
        }
        sum += d;
    }
    else {
        for (int j = 0; j < m - 1; j++) {
            sum += b[j];
        }
        sum += d;
    }
    
    printf("%d年%d月%d日是这一年的第%d天\n", y, m, d, sum);

给定某年某月某日,输出其为这一年的第几天。