题目链接https://www.luogu.com.cn/problem/P8651

枚举

最好用上tuple来存三元的
也许有更好的方法，我写的比较复杂

#include <iostream>
#include <string>
#include <cstring>
#include <algorithm>
#include <set>
#include <map>
#include <tuple>

#define ll long long

const ll N = 1e5 + 10;
//ll n,m;
//ll op[N];

struct ii{
    ll ye;
    ll mo;
    ll da;
    friend bool operator<(ii &w1,ii &w2){
        if(w1.ye != w2.ye)
        return w1.ye < w2.ye;
        else{
            if(w1.mo != w2.mo) return w1.mo < w2.mo;
            else{
                return w1.da < w2.da;
             }
         }
    }
}pp[N];

bool check1(ll yy){
    if(yy % 400 == 0 || (yy % 4 == 0 && yy % 100 != 0)) return true;
    else return false;
}

bool check(ll yy,ll mm,ll dd){
    if(mm > 12 || mm < 1) return false;
    if(dd > 31 || dd < 1) return false;
    if(mm == 1 || mm == 3 || mm == 5 || mm == 7 || mm == 8 || mm == 10 || mm == 12){
        if(dd >= 1 && dd <= 31) return true;
        else return false;
    }
    if(mm == 4 || mm == 6 || mm == 9 || mm == 11){
        if(dd >= 1 && dd <= 30) return true;
        else return false;
    }
    if(check1(yy)){//闰月
        if(dd >= 1 && dd <= 29) return true;
        else return false;
    }
    else{
        if(dd >= 1 && dd <= 28) return true;
        else return false;
    }
}

void solve(){
    std::string a;
    std::cin >> a;
    std::map<std::tuple<ll,ll,ll>,ll> op;
    std::string aa = a.substr(0,2);
    std::string bb = a.substr(3,2);
    std::string cc = a.substr(6,2);
    std::string dp[] = {aa,bb,cc};
    ll re = 0;
    for(ll i = 0; i <= 2; i ++){
        for(ll j = 0; j <= 2; j ++){
            for(ll k = 0; k <= 2; k ++){
                if(i != j && i != k && j != k){
                    if(i == 0 && j > k) continue;
                    if(i == 1) continue;
                    ll uu = std::stoll(dp[i]);
                    std::string a1;
                    if(uu >= 60){
                        a1 = "19" + dp[i];
                    }
                    else a1 = "20" + dp[i];
                    ll y1 = std::stoll(a1);
                    ll m1 = std::stoll(dp[j]);
                    ll d1 = std::stoll(dp[k]);
//                  std::cout << y1 << " " << m1 << " " << d1 << "\n";
                    if(check(y1,m1,d1)){
//                      std::cout << "正确的\n";
                        if(op[{y1,m1,d1}] == 0){
                            pp[++re] = {y1,m1,d1};

//                          printf("%.4lld-%.2lld-%.2lld\n",y1,m1,d1);
                        }
                        op[{y1,m1,d1}] ++;
                    }
                }
            }
        }
    }
    std::sort(pp + 1,pp + 1 + re);
    for(ll i = 1; i <= re; i ++){
        printf("%.4lld-%.2lld-%.2lld\n",pp[i].ye,pp[i].mo,pp[i].da);
    }
    return ;
}

int main(){
    ll t = 1;
    while(t --)
    solve();
    return 0;
}