Submission #1247584

#	Time	Username	Problem	Language	Result	Execution time	Memory
1247584		erering	Thousands Islands (IOI22_islands)	C++20	6.75 / 100	1094 ms	31560 KiB

islands

#include <bits/stdc++.h>
#include "islands.h"
using namespace std;
#define pb push_back
const int MAXN=1000+5;
bool vis[MAXN],vis2[MAXN];
vector<int> adj[MAXN][MAXN];
vector<int> path;
bool dfs(int node,int par){
    if(vis[node])return 0;
    vis[node]=1;
    for(int j=0;j<MAXN;j++){
        if(j==par)continue;
        if(adj[node][j].size()>1 && adj[j][node].size()>0){
            path.pb(adj[node][j][0]);
            path.pb(adj[j][node][0]);
            path.pb(adj[node][j][1]);
            path.pb(adj[node][j][0]);
            path.pb(adj[j][node][0]);
            path.pb(adj[node][j][1]);
            return 1;
        }
    }
    for(int j=0;j<MAXN;j++){
        if(j==par)continue;
        if(adj[node][j].size()>0){
            path.pb(adj[node][j][0]);
            bool flag=dfs(j,node);
            if(flag){
                path.pb(adj[node][j][0]);
                return 1;
            }
            else path.pop_back();
        }
    }
    return 0;
}
vector<int> cycle;
int dfs2(int node,int par){
    vis2[node]=1;
    for(int j=0;j<MAXN;j++){
        if(j==par || adj[node][j].size()==0)continue;
        if(vis2[j]){
            cycle.pb(node);
            return j;
        }
        int x=dfs2(j,node);
        if(x==-2){
            path.pb(adj[node][j][0]);
            return -2;
        }
        if(x!=-1){
            cycle.pb(node);
            if(x==node)return -2;
            return x;
        }
    }
    vis2[node]=0;
    return -1;
}
variant<bool, vector<int>> find_journey(int N, int M, vector<int> U, vector<int> V) {
    for(int i=0;i<M;i++){
        if(adj[U[i]][V[i]].size()<2)adj[U[i]][V[i]].pb(i);
    }
    bool flag=dfs(0,-1);
    if(!flag){
        for(int i=1;i<=N;i++)vis[i]=0;
        dfs2(0,-1);
        if(cycle.empty())return false;
        else{
            reverse(path.begin(),path.end());
            reverse(cycle.begin(),cycle.end());
         /*   for(auto i:path)cout<<i<<' ';
            cout<<'s'<<endl;
           /* for(auto i:cycle)cout<<i<<' ';
            cout<<endl<<endl;*/
            vector<int> final=path,rev[2];
            for(int t=0;t<2;t++) {
                for (int id = 0; id < cycle.size() ; id++) {
                    int i = cycle[id];
                    int i2 = cycle[(id + 1)%cycle.size()];
                    rev[t].pb(adj[i][i2][t]);
                    final.pb(adj[i][i2][t]);
                }
            }
            reverse(rev[0].begin(),rev[0].end());
            reverse(rev[1].begin(),rev[1].end());
            for(int t=0;t<2;t++){
                for(auto i:rev[t])final.pb(i);
            }
            for(int i=path.size()-1;i>=0;i--)final.pb(path[i]);
            return final;
        }
    }
    return path;
}

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