Submission #1070308

#	Time	Username	Problem	Language	Result	Execution time	Memory
1070308		Unforgettablepl	Thousands Islands (IOI22_islands)	C++17	24 / 100	26 ms	6352 KiB

islands

#include "islands.h"
#include <bits/stdc++.h>
using namespace std;

variant<bool, vector<int>> find_journey(int N,int M,vector<int> U,vector<int> V){
    vector<vector<pair<int,int>>> adj(N);
    for(int i=0;i<M;i+=2) {
        adj[U[i]].emplace_back(V[i],i);
    }
    vector<int> visited(N);
    stack<int> path;
    function<bool(int)> dfs = [&](int x) {
        if(visited[x]==2)return false;
        if(visited[x]==1){
            return true;
        }
        visited[x]=1;
        for(auto&[v,idx]:adj[x]) {
            path.emplace(idx);
            if(dfs(v))return true;
            path.pop();
        }
        visited[x]=2;
        return false;
    };
    if(!dfs(0))return false;
    vector<int> path_cycle,path_direct;
    int ver = V[path.top()];
    bool phase = false;
    while(!path.empty()) {
        int curr = path.top();path.pop();
        if(!phase)path_cycle.emplace_back(curr);
        else path_direct.emplace_back(curr);
        if(U[curr]==ver)phase=true;
    }
    reverse(path_cycle.begin(),path_cycle.end());
    reverse(path_direct.begin(),path_direct.end());
    vector<int> ans = path_direct;
    for(int&i:path_cycle)ans.emplace_back(i);
    for(int&i:path_cycle)ans.emplace_back(i+1);
    reverse(path_cycle.begin(), path_cycle.end());
    for(int&i:path_cycle)ans.emplace_back(i);
    for(int&i:path_cycle)ans.emplace_back(i+1);
    reverse(path_direct.begin(),path_direct.end());
    for(int&i:path_direct)ans.emplace_back(i);
    return ans;
}

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