Submission #830772

#	Time	Username	Problem	Language	Result	Execution time	Memory
830772		FatihSolak	Thousands Islands (IOI22_islands)	C++17	55 / 100	137 ms	27392 KiB

islands

#include "islands.h"
#include <bits/stdc++.h>
#define N 100005
using namespace std;
vector<pair<int,pair<int,int>>> adj[N];
map<int,vector<int>> mp[N];
int par[N];
int par2[N];
int vis[N];
vector<int> ans;
void dfs(int v,int pr){
	vis[v] = 1;
	vector<pair<int,pair<int,int>>> tmp;
	for(auto u:adj[v]){
		if(ans.size())
			return;
		if(u.second.second == pr)
			continue;
		if(vis[u.first] == 2)
			continue;
		tmp.push_back(u);
	}
	if(tmp.size() > 1){
		int now = v;
		while(now != 0){
			ans.push_back(par[now]);
			now = par2[now];
		}
		reverse(ans.begin(),ans.end());
		ans.push_back(tmp[0].second.first);
		ans.push_back(tmp[0].second.second);
		ans.push_back(tmp[1].second.first);
		ans.push_back(tmp[1].second.second);
		ans.push_back(tmp[0].second.second);
		ans.push_back(tmp[0].second.first);
		ans.push_back(tmp[1].second.second);
		ans.push_back(tmp[1].second.first);
		now = v;
		while(now != 0){
			ans.push_back(par[now]);
			now = par2[now];
		}
		return;
	}
	else{
		for(auto u:adj[v]){
			if(ans.size())
				return;
			if(vis[u.first])
				continue;
			par[u.first] = u.second.first;
			par2[u.first] = v;
			dfs(u.first,u.second.first);
		}
	}
	vis[v] = 2;
}
void dfs2(int v,int pr){
	vis[v] = 1;
    // cout << v << ' ' << par2[v] << endl; 
	vector<pair<int,pair<int,int>>> tmp;
	for(auto u:adj[v]){
		if(ans.size())
			return;
		if(vis[u.first] == 2){
			continue;
		}
		if(vis[u.first] == 1){
            if(ans.size())
                return;
            // cout << u.first << "ASDa" << v << endl;
            int now = u.first;
            while(now != 0){
                ans.push_back(par[now]);
                now = par2[now];
            }
            reverse(ans.begin(),ans.end());
            vector<int> v1 = {},v2 = {};
            now = v;
            int cnt = 0;
            int sz = 1;
            while(now != u.first){
                assert(cnt++ <= 1000);
                v1.push_back(par[now]);
                v2.push_back(par[now] + 1);
                sz++;
                // cout << now << endl;
                now = par2[now];
            }
            reverse(v1.begin(),v1.end());
            reverse(v2.begin(),v2.end());
            v1.push_back(u.second.first);
            v2.push_back(u.second.first + 1);
            assert(sz >= 2);
            for(auto c:v1){
                ans.push_back(c);
            }
            for(auto c:v2){
                ans.push_back(c);
            }
            reverse(v1.begin(),v1.end());
            reverse(v2.begin(),v2.end());
            for(auto c:v1){
                ans.push_back(c);
            }
            for(auto c:v2){
                ans.push_back(c);
            }
            now = u.first;
            while(now != 0){
                ans.push_back(par[now]);
                now = par2[now];
            }
			return;
        }
		par[u.first] = u.second.first;
		par2[u.first] = v;
		dfs2(u.first,u.second.first);
	}
	vis[v] = 2;
}
variant<bool, vector<int>> find_journey(int n, int m, vector<int> U, vector<int> V){
	if(n == 2){
		for(int i = 0;i<m;i++){
			mp[U[i]][V[i]].push_back(i);
		}
		if(mp[0][1].size() < 2 || mp[1][0].size() < 1)
			return false;
		int a = mp[0][1][0];
		int b = mp[0][1][1];
		int c = mp[1][0][0];
		ans = {a,c,b,a,c,b};
		return ans;
	}
	bool subtask4 = (m + 1)%2;
	for(int i = 0;i<m && subtask4;i+=2){
		if(U[i] != U[i+1] || V[i] != V[i+1])
			subtask4 = 0;
	}
	if(subtask4){
		for(int i = 0;i<m;i+=2){
			adj[U[i]].push_back({V[i],{i,i+1}});	
			// cout << U[i] << ' ' << V[i] << endl;
		}
		dfs2(0,-1);
		if(!ans.size())
			return false;
		return ans;
	}
	for(int i = 0;i<m;i++){
		if(mp[V[i]][U[i]].size()){
			adj[U[i]].push_back({V[i],{i,mp[V[i]][U[i]].back()}});
			adj[V[i]].push_back({U[i],{mp[V[i]][U[i]].back(),i}});
			mp[V[i]][U[i]].pop_back();
		}else{
			mp[U[i]][V[i]].push_back(i);
		}
	}
	dfs(0,-1);
	if(ans.empty())
		return false;
	return ans;
}

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