Submission #628551

#	Time	Username	Problem	Language	Result	Execution time	Memory
628551		qwerasdfzxcl	Thousands Islands (IOI22_islands)	C++17	35 / 100	331 ms	32400 KiB

islands

#include "islands.h"
#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
set<pair<int, int>> adj[100100], INV[100100];
vector<int> deg0, ansf, ansb;
int n, s, on[100100];

void _erase(int x){
    if (!on[x]) return;
    on[x] = 0;
    for (auto &[v, i]:INV[x]){
        adj[v].erase(adj[v].find(make_pair(x, i)));
        if (adj[v].empty()) deg0.push_back(v);
    }
    for (auto &[v, i]:adj[x]) INV[v].erase(INV[v].find(make_pair(x, i)));
}


std::variant<bool, std::vector<int>> find_journey(
    int N, int M, std::vector<int> U, std::vector<int> V) {

    n = N, s = 1;
    fill(on+1, on+n+1, 1);
    for (int i=0;i<M;i++){
        ++U[i], ++V[i];
        adj[U[i]].emplace(V[i], i+1);
        INV[V[i]].emplace(U[i], i+1);
    }

    for (int i=1;i<=n;i++) if (adj[i].empty()) deg0.push_back(i);
    while(true){
        while(!deg0.empty()){
            int x = deg0.back(); deg0.pop_back();
            _erase(x);
        }
        if (!on[s]) return false;
        if (adj[s].size()>1) break;

        ansf.push_back(adj[s].begin()->second);
        ansb.push_back(adj[s].begin()->second);
        int nxt = adj[s].begin()->first;
        _erase(s);
        s = nxt;
    }

    return true;
}

• Subtask 1: 1.75 / 5
• Subtask 2: 1.75 / 5
• Subtask 3: 7.35 / 21
• Subtask 4: 8.399999999999999 / 24
• Subtask 5: 15.749999999999998 / 45