Submission #824281

#	Time	Username	Problem	Language	Result	Execution time	Memory
824281		Liudas	Thousands Islands (IOI22_islands)	C++17	18.40 / 100	299 ms	6476 KiB

islands

#include "islands.h"
#include <cassert>
#include <cstdio>
#include <variant>
#include <vector>
#include <algorithm>
#include <iostream>
using namespace std;
bool loop = false;
void dfs(int node, vector<vector<pair<int, int>>> &tree, vector<bool> &vis){
    if(vis[node]){
        loop = true;
        return;
    }
    vis[node] = true;
    for(auto&[l, r] : tree[node]){
        if(!r){
            r = true;
            dfs(l, tree, vis);
        }
    }
    vis[node] = false;
}
variant<bool, vector<int>> find_journey(int N, int M, vector<int> U, vector<int> V) {
    if (N == 2){
        if(count(U.begin(), U.end(), 0) >= 2 && count(U.begin(), U.end(), 1) >= 1){
            vector<pair<int, int>> ans(M);
            for(int i = 0; i < M; i ++){
                ans[i] = {U[i], i};
            }
            sort(ans.begin(), ans.end());
            vector<int> ret = {ans[0].second, ans.back().second, ans[1].second, ans[0].second, ans.back().second, ans[1].second};
            return ret;
        }
        return false;
    }
    bool N2 = true;
    for(int i = 0; i < N; i ++){
        N2 &= ((count(U.begin(), U.end(), i) + count(V.begin(), V.end(), i)) == 2 * N - 2);
    }
    if(N2){
        vector<vector<pair<int, int>>> tree(N);
        for(int i = 0; i < M; i ++){
            tree[U[i]].push_back({V[i], i});
        }
        for(int i = 0; i < N; i ++){
            sort(tree[i].begin(), tree[i].end());
        }
        vector<int> ret = {tree[0][0].second, tree[1][0].second, tree[0][1].second, tree[2][0].second, tree[1][0].second, tree[0][0].second, tree[2][0].second, tree[0][1].second};
        return ret;
    }
    vector<vector<pair<int,int>>> tree(N);
    tree.clear();
    tree.assign(N, {});
    for(int i = 0; i < M; i ++){
        tree[U[i]].push_back({V[i], 0});
    }
    vector<bool> vis(N, 0);
    dfs(0, tree, vis);
    vector<int> arr(3, 0);
    if(loop){
        return arr;
    }
    return false;
}

• Subtask 1: 5 / 5
• Subtask 2: 5 / 5
• Subtask 3: 0 / 21
• Subtask 4: 8.399999999999999 / 24
• Subtask 5: 0 / 45