Submission #1239599

#	Time	Username	Problem	Language	Result	Execution time	Memory
1239599		matsakyannn	Thousands Islands (IOI22_islands)	C++20	1.75 / 100	18 ms	7240 KiB

islands

#include <bits/stdc++.h>
#include <variant>
using namespace std;

#ifndef ONLINE_JUDGE
#define dbg(x) cerr << #x << ' '; print(x); cerr << endl;
#else
#define dbg(x)
#endif 

void print(int x) {cerr << x;}
void print(long long x) {cerr << x;}
void print(char x) {cerr << x;}
void print(string x) {cerr << x;}
void print(double x) {cerr << x;}
template <class T> void print(vector <T> x);
template <class T> void print(set <T> x);
template <class T> void print(multiset <T> x);
template <class T, class V> void print(pair <T, V> x);
template <class T, class V> void print(map <T, V> x);
template <class T> void print(vector <T> x) {cerr << "[ "; for(auto i : x) {print(i); cerr << ' ';} cerr << "]";}
template <class T> void print(set <T> x) {cerr << "[ "; for(auto i : x) {print(i); cerr << ' ';} cerr << "]";}
template <class T> void print(multiset <T> x) {cerr << "[ "; for(auto i : x) {print(i); cerr << ' ';} cerr << "]";}
template <class T, class V> void print(pair <T, V> x) {cerr << "{"; print(x.first); cerr << ' '; print(x.second); cerr << "}";}
template <class T, class V> void print(map <T, V> x) {cerr << "[ "; for(auto i : x) {print(i); cerr << ' ';} cerr << "]";}

#define ll long long
#define pb push_back
#define ppb pop_back
#define PII pair <int, int>
#define PLL pair <ll, ll>
#define all(v) (v).begin(), (v).end()
#define OK cerr << "OK\n";
#define MP make_pair

const int N0 = 1005, M0 = 2e5 + 5;
int n, m, kayak[N0][N0], revkayak[M0];
vector <int> u, v;
vector <int> G[N0];

vector <int> color, cycle, road;
int par[N0];
void dfs(int node, int parent){
    par[node] = parent;
    color[node] = 1;
    for(int u : G[node]){
        if(u == parent) continue;
        if(color[u] == 0){
            dfs(u, node);
            if(!cycle.empty()) return;
            continue;
        }
        if(color[u] == 1){
            int curr = node;
            while(curr != par[u]){
                cycle.pb(curr);
                curr = par[curr];
            }
            curr = u;
            while(curr != -1){
                road.pb(curr);
                curr = par[curr];
            }
            return;
        }
    }
}

variant <bool, vector <int>> find_journey(int N, int M, vector<int> U, vector<int> V){
    if(N == 2) return false;
    for(int i = 0; i < N; i++){
        for(int j = 0; j < N; j++){
            kayak[i][j] = -1;
        }
    }
    n = N, m = M, u = U, v = V;
    for(int i = 0; i < M; i++){
        G[u[i]].pb(v[i]);
        kayak[u[i]][v[i]] = i;
    }
    for(int i = 0; i < N; i++){
        for(int j = 0; j < N; j++){
            if(kayak[i][j] == -1) continue;
            revkayak[kayak[i][j]] = kayak[j][i]; 
        }
    }

    color.assign(N, 0);
    dfs(0, -1);
    if(!cycle.empty()){
        vector <int> res;
        reverse(all(road));
        for(int i = 0; i < int(road.size() - 1); i++){
            res.pb(kayak[road[i]][road[i + 1]]);
        }
        reverse(all(cycle));
        for(int i = 1; i < cycle.size(); i++){
            res.pb(kayak[cycle[i - 1]][cycle[i]]);
        }
        res.pb(kayak[cycle.back()][cycle.front()]);
        res.pb(kayak[cycle.front()][cycle.back()]);
        for(int i = cycle.size() - 1; i >= 1; i--){
            res.pb(kayak[cycle[i]][cycle[i - 1]]);
        }
        int sz = res.size();
        for(int i = sz - cycle.size(); i < sz; i++){
            res.pb(revkayak[res[i]]);
        }
        for(int i = road.size(); i < road.size() + cycle.size(); i++){
            res.pb(revkayak[res[i]]);
        }
        for(int i = int(road.size() - 1); i >= 1; i--){
            res.pb(kayak[road[i - 1]][road[i]]);
        }
        return res;
    }
}

Compilation message (stderr)

islands.cpp: In function 'std::variant<bool, std::vector<int, std::allocator<int> > > find_journey(int, int, std::vector<int>, std::vector<int>)':
islands.cpp:117:1: warning: control reaches end of non-void function [-Wreturn-type]
  117 | }
      | ^

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