c语言任务 05-05-13 日期识别3

Question

任务05-05-13 日期识别3
怎么写，快崩溃了，不知道从哪下手。碰过类似的题，前面的题还好，到这里不会了。

Answer 1

供参考：

#include<stdio.h>
int is_leap_year(int y)  // 判断是否闰年
{
    return ((y % 4 == 0 && y % 100 != 0) || y % 400 == 0);
}
int DaysOfMonth(int y, int m) // 某月的天数
{
    int days[12] = { 31,28,31,30,31,30,31,31,30,31,30,31 };
    if (is_leap_year(y) && m == 2)
        return  days[m - 1] + 1;
    return days[m - 1];
}
int is_valid_date(int y, int m, int d) //判断日期是否合法
{ 
    if (y < 1 || y > 9999 || m < 1 || m > 12 || d < 1 || d > 31)
        return 0;
    return  d <= DaysOfMonth(y, m);
}
void compare(int* a, int* b, int* c)
{
    int t;
    if (*a > *b) t = *a, * a = *b, * b = t;
    if (*a > *c) t = *a, * a = *c, * c = t;
    if (*b > *c) t = *b, * b = *c, * c = t;
}
int main()
{
    int a, b, c, num = 0, valid_date[6][3] = { 0 };
    scanf("%d%*c%d%*c%d", &a, &b, &c);
    compare(&a, &b, &c);
    if (is_valid_date(a, b, c)) {
        valid_date[num][0] = a;
        valid_date[num][1] = b;
        valid_date[num][2] = c;
        num++;
    }
    if (is_valid_date(a, c, b) && b != c) {
        valid_date[num][0] = a;
        valid_date[num][1] = c;
        valid_date[num][2] = b;
        num++;
    }
    if (is_valid_date(b, a, c) && a != b) {
        valid_date[num][0] = b;
        valid_date[num][1] = a;
        valid_date[num][2] = c;
        num++;
    }
    if (is_valid_date(b, c, a) && c != b) {
        valid_date[num][0] = b;
        valid_date[num][1] = c;
        valid_date[num][2] = a;
        num++;
    }
    if (is_valid_date(c, a, b) && a != c && b != c)
    {
        valid_date[num][0] = c;
        valid_date[num][1] = a;
        valid_date[num][2] = b;
        num++;
    }
    if (is_valid_date(c, b, a) && a != c && a != b) {
        valid_date[num][0] = c;
        valid_date[num][1] = b;
        valid_date[num][2] = a;
        num++;
    }
    if (num == 0) 
        printf("Invalid Date!");
    else {
        printf("%d\n", num);
        for (num--; num >= 0; num--) {
            printf("%04d-%02d-%02d", valid_date[num][0], valid_date[num][1], valid_date[num][2]);
            if (num)  printf("\n");
        }
    }
    return 0;
}