题解 | 日期差值

#include <iostream>
using namespace std;

int main() {
    int m;
    int n;
    cin >> m;
    cin >> n;
    int a = min(m, n);
    int b = max(m, n);
    int ans = 0;
    int x = a / 10000; //year；
    int y = b / 10000;
    int z = a / 100 % 100; //month
    int w = b / 100 % 100;
    int k = a % 100; //day
    int p = b % 100;
    int f[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
    if (x == y) { //year equal;
        if (x % 400 == 0 || (x % 4 == 0 && x % 100 != 0)) f[1] = 29;
        if (z == w) { //day equal
            ans = p - k + 1;
        } else {
            ans += f[z - 1] - k;
            for (int i = z; i < w - 1; i++) {
                ans += f[i];
            }
            ans += p + 1;
        }
    } else {
        if (x % 400 == 0 || (x % 4 == 0 && x % 100 != 0))f[1] = 29; //run year
        ans += f[z - 1] - k;
        for (int i = z; i < 12; i++) {
            ans += f[i];
        }
        for (int i = x + 1; i < y; i++) {
            if (i % 400 == 0 || (i % 4 == 0 && i % 100 != 0))ans += 366;
            else ans += 365;
        }
        f[1] = 28;
        if (y % 400 == 0 || (y % 4 == 0 && y % 100 != 0)) f[1] = 29;
        for (int i = 0; i < w - 1; i++)
            ans += f[i];
        ans += p + 1;
    }
    cout << ans << endl;
}
// 64 位输出请用 printf("%lld")