Submission #826407

#	Time	Username	Problem	Language	Result	Execution time	Memory
826407		alvingogo	Thousands Islands (IOI22_islands)	C++17	9.10 / 100	27 ms	6400 KiB

islands

#include "islands.h"
#include <bits/stdc++.h>
#include <variant>
#define fs first
#define sc second
using namespace std;

vector<vector<pair<int,int> > > e;
vector<int> dep,fa;
vector<int> ss;
vector<int> ans;
int dfs(int r,int f){
    dep[r]=dep[f]+1;
    fa[r]=f;
    for(auto h:e[r]){
        if(ss[h.sc/2]){
            continue;
        }
        ss[h.sc/2]=1;
        if(dep[h.fs]==-1){
            if(dfs(h.fs,r)){
                return 1;
            }
        }
        else if(dep[h.fs]>=0){
            return 1;
        }
    }
    dep[r]=-2;
    return 0;
}
variant<bool, vector<int>> find_journey(
    int n, int m, vector<int> u, vector<int> v) {
    e.resize(n);
    fa.resize(n);
    ss.resize(m);
    dep.resize(n,-1);
    for(int i=0;i<m;i++){
        e[u[i]].push_back({v[i],i});
    }
    dfs(0,0);
    ans.clear();
    if(e[0].size()>=2){
        ans={e[0][0].sc,e[0][0].sc^1,e[0][1].sc,e[0][1].sc^1,e[0][0].sc^1,e[0][0].sc,e[0][1].sc^1,e[0][1].sc};
        return ans;
    }
    for(int i=1;i<n;i++){
        if(dep[i]!=-1){
            if(e[i].size()>=3){
                vector<int> bz;
                vector<int> vs(m);
                for(int j=i;j!=0;){
                    for(auto w:e[j]){
                        if(fa[j]==w.fs){
                            bz.push_back(w.sc);
                            vs[w.sc/2]=1;
                            j=w.fs;
                            break;
                        }
                    }
                }
                int ct=0;
                vector<int> y;
                ans.insert(ans.end(),bz.begin(),bz.end());
                for(auto h:e[i]){
                    if(!vs[h.sc/2]){
                        ct++;
                        y.push_back(h.sc);
                        if(ct==2){
                            break;
                        }
                    }
                }
                ans.push_back(y[0]);
                ans.push_back(y[0]^1);
                ans.push_back(y[1]);
                ans.push_back(y[1]^1);
                
                ans.push_back(y[0]^1);
                ans.push_back(y[0]);
                ans.push_back(y[1]^1);
                ans.push_back(y[1]);
                reverse(bz.begin(),bz.end());
                ans.insert(ans.end(),bz.begin(),bz.end());
                return ans;
            }
        }
    }
    return false;
}

• Subtask 1: 0 / 5
• Subtask 2: 1.75 / 5
• Subtask 3: 7.35 / 21
• Subtask 4: 0 / 24
• Subtask 5: 0 / 45