Submission #1069385

#	Time	Username	Problem	Language	Result	Execution time	Memory
1069385		mariaclara	Thousands Islands (IOI22_islands)	C++17	1.75 / 100	26 ms	8788 KiB

islands

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

using namespace std;

typedef long long ll;
typedef pair<int,int> pii;
#define all(x) x.begin(), x.end()
#define sz(x) (int)x.size()
#define pb push_back
#define mk make_pair
#define fr first
#define sc second

vector<int> ord, vis, valid;
vector<vector<pii>> edges, tedges;

void dfs(int x) {
    vis[x] = 1;
    for(auto [viz,ind] : edges[x])
        if(!vis[viz]) dfs(viz);
    ord.pb(x);
}

void find_scc(int x) {
    vis[x] = 1;
    for(auto [viz, ind] : tedges[x]) {
        if(!vis[viz]) {
            valid[x] = valid[viz] = 1;
            find_scc(viz);
        } 
    }
}

variant<bool, vector<int>> find_journey(int N, int M, vector<int> U, vector<int> V) {
    edges.resize(N);
    tedges.resize(N);
    vis.resize(N);
    valid.resize(N);

    for(int i = 0; i < M; i++)  edges[U[i]].pb({V[i], i}), tedges[V[i]].pb({U[i], i});

    //cout << "OK" << endl;
    for(int i = 0; i < N; i++)
        if(!vis[i]) dfs(i);

    reverse(all(ord));
    vis.clear();  vis.resize(N);

    for(auto x : ord)
        if(!vis[x]) find_scc(x);


    // agora basta ver se tem como chegar em um no valido de 2 formas

    vector<vector<int>> s(N);
    queue<pii> fila;
    fila.push({0,-1});

    while(!fila.empty()) {
        auto [x, s_e] = fila.front();
        fila.pop();

        if(sz(s[x]) >= 2) continue;
        if(sz(s[x]) == 1 and s[x][0] == s_e) continue;
        if(s_e != -1) s[x].pb(s_e);

        for(auto [viz, ind] : edges[x]) {
            if(s_e == -1) fila.push({viz, ind});
            else fila.push({viz, s_e});
        }
    }

    if(sz(edges[0]) >= 2) return vector<int>({1});
    for(int i = 0; i < N; i++)
        if(sz(s[i]) >= 2 and valid[i]) return vector<int>({1});

    return false;
}

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