Submission #764318

#	Time	Username	Problem	Language	Result	Execution time	Memory
764318		raysh07	Thousands Islands (IOI22_islands)	C++17	9.10 / 100	83 ms	14472 KiB

islands

#include "islands.h"
#include <variant>
#include <bits/stdc++.h>
using namespace std;
 
const int N = 1001;
int deg[N];
bool vis[N];
vector <pair<int, int>> adj[N];
vector <int> path, ok;
map <pair<int, int> , int> mp;
int n;
 
void dfs(int u){
    vis[u] = true;
    path.push_back(u);
    if (deg[u] >= 3 && ok.size() == 0){
        ok = path;
    }
    for (auto [v, i] : adj[u]){
        if (!vis[v]) dfs(v);
    }
    path.pop_back();
}
 
void get(vector <int> &ans, int x, int y){
    ans.push_back(x);
    ans.push_back(x ^ 1);
    ans.push_back(y);
    ans.push_back(y ^ 1);
    ans.push_back(x ^ 1);
    ans.push_back(x);
    ans.push_back(y ^ 1);
    ans.push_back(y);
}
 
variant<bool, vector<int>> find_journey(int nn, int m, vector<int> u, vector<int> v) {
    n = nn;
    for (int i = 0; i < m; i++){
        adj[u[i]].push_back({v[i], i});
        mp[{u[i], v[i]}] = i;
        deg[u[i]]++;
    }
    
    vector <int> ans;
    
    if (deg[0] >= 2){
        int v1 = adj[0][0].second;
        int v2 = adj[0][1].second;
        
        get(ans, v1, v2);
        return ans;
    } 
    
    dfs(0);
    if (ok.size() == 0) return false;
    
    vector <int> a1;
    for (int i = 1; i < ok.size(); i++) a1.push_back(mp[{ok[i - 1], ok[i]}]);
    ans = a1;
    int v1, v2, v3, x, y;
    x = ok.back();
    ok.pop_back();
    y = a1.back();
    
    v1 = adj[x][0].second;
    v2 = adj[x][1].second;
    v3 = adj[x][2].second;
    
    if (v1 != y && v2 != y) get(ans, v1, v2);
    else if (v1 == y) get(ans, v2, v3);
    else get(ans, v1, v3);
    
    reverse(a1.begin(), a1.end());
    for (auto x : a1) ans.push_back(x);
    
    map <int, int> hol;
    for (auto x : ans) hol[x]++;
    
    for (auto [x, y] : hol) if (y & 1) assert(false);
    return ans;
}

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:59:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   59 |     for (int i = 1; i < ok.size(); i++) a1.push_back(mp[{ok[i - 1], ok[i]}]);
      |                     ~~^~~~~~~~~~~

• Subtask 1: 0 / 5
• Subtask 2: 1.75 / 5
• Subtask 3: 7.35 / 21
• Subtask 4: 0 / 24
• Subtask 5: 0 / 45