第十一届蓝桥杯c++B组第二场第四题

emm…经典处理日期的问题，开一个月份M数组即可

方法一:

#include<iostream>

using namespace std;

int y = 2000,m = 1,d = 1,w = 6,ans = 2;     //定义年，月，日，星期w
int M[13] = {0,31,28,31,30,31,30,31,31,30,31,30,31};

int main()
{
    while(y != 2020 || m != 10 || d != 1)
    {
        if((y % 4 == 0 && y % 100 != 0) || y % 400 == 0) M[2] = 29;
        else M[2] = 28;               //这里else不能丢，因为要保证每一年都要更新M[2]
        d++;
        w = (w + 1) % 7;

        if(d>M[m])
        {
            d = 1;
            m++;
            if(m > 12)
            {
                m = 1;
                y++;
            }
        }

        if(d == 1 || w == 1) ans++;

        ans++;
    }

    cout<<ans;
    return 0;
}

方法二:

#include<iostream>

using namespace std;

typedef long long LL;

LL res,Monday;
int days[13] = {0,31,28,31,30,31,30,31,31,30,31,30,31};

bool is_vaild(int x)
{
    int yy = x/10000,mm = x%10000/100,day = x%100;
    if(mm < 1 || mm > 12) return false;
    if(day <= 0) return false;
    if(mm != 2)
    {
        if(day > days[mm]) return false;
    }
    else
    {
        int leap =((yy % 4 == 0 && yy % 100 != 0) || (yy % 400 == 0));
        if(day > 28 + leap) return false;
    }
    return true;
}

int main()
{
    int w = 5;
    for(int i = 20000101;i <= 20201001;i++)
    {
        int yy = i/10000,mm = i%10000/100,dd = i%100;
        if(!is_vaild(i)) continue;     //一定要先判断日期是否合法再进行星期的变换，不然星期会乱套！！！
        else                           //(ps:这个细节看了我三天硬是没找出来,一直是8877少答案2,低级错误)
        {
         w = (w + 1) % 7;
         if(dd == 1 || w == 1) res++;
         res++;
        }
    }

    cout<<res;
}