Submission #825744

#	Time	Username	Problem	Language	Result	Execution time	Memory
825744		ttamx	Thousands Islands (IOI22_islands)	C++17	24 / 100	30 ms	7172 KiB

islands

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

using namespace std;

const int N=1e5+5;
const int M=2e5+5;

int n,m;
vector<pair<int,int>> adj[N];
vector<int> path;
bool vis[N],vis2[N];

int dfs(int u){
	if(vis2[u])return u;
	if(vis[u])return -1;
	vis[u]=vis2[u]=true;
	for(auto [v,id]:adj[u]){
		path.emplace_back(id);
		int res=dfs(v);
		if(res!=-1)return res;
		path.pop_back();
	}
	vis2[u]=false;
	return -1;
}

variant<bool, vector<int>> find_journey(int N,int M,vector<int> U,vector<int> V){
	n=N,m=M;
	for(int i=0;i<m;i+=2)adj[U[i]].emplace_back(V[i],i);
	int res=dfs(0);
	if(res==-1)return false;
	auto ans=path;
	vector<int> path2;
	stack<int> rev;
	int cur=0;
	bool ok=false;
	for(auto i:path){
		if(cur==res)ok=true;
		if(!ok){
			rev.emplace(i);
		}else{
			path2.emplace_back(i);
		}
		cur=V[i];
	}
	for(auto i:path2){
		ans.emplace_back(i+1);
	}
	reverse(path2.begin(),path2.end());
	for(auto i:path2){
		ans.emplace_back(i);
	}
	for(auto i:path2){
		ans.emplace_back(i+1);
	}
	while(!rev.empty()){
		ans.emplace_back(rev.top());
		rev.pop();
	}
	return ans;
}

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