Submission #836352

#	Time	Username	Problem	Language	Result	Execution time	Memory
836352		SamAnd	Thousands Islands (IOI22_islands)	C++17	6.75 / 100	26 ms	5972 KiB

islands

#include "islands.h"
#include <variant>
#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define m_p make_pair
#define all(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
typedef long long ll;
const int N = 1003, M = 200005;

vector<pair<int, int> > g[N];

bool c[N];
int p[N];
int pi[N];
vector<int> ans;
bool dfs(int x)
{
    c[x] = true;
    for (int i = 0; i < g[x].size(); ++i)
    {
        int h = g[x][i].fi;
        int hi = g[x][i].se;
        if (hi / 2 == pi[x] / 2)
            continue;
        if (!c[h])
        {
            p[h] = x;
            pi[h] = hi;
            if (dfs(h))
                return true;
        }
        else
        {
            return true;
        }
    }
}

std::variant<bool, std::vector<int> > find_journey(int N, int M, std::vector<int> U, std::vector<int> V)
{
    for (int i = 0; i < M; ++i)
    {
        g[U[i]].push_back(m_p(V[i], i));
    }
    if (N == 2)
    {
        if (sz(g[0]) >= 2 && sz(g[1]) >= 1)
        {
            ans.push_back(g[0][0].se);
            ans.push_back(g[1][0].se);
            ans.push_back(g[0][1].se);
            ans.push_back(g[0][0].se);
            ans.push_back(g[1][0].se);
            ans.push_back(g[0][1].se);
            return ans;
        }
        return false;
    }

    p[0] = -3;
    pi[0] = -3;
    return dfs(0);
    /*if (!dfs(0))
        return false;
    return ans;*/
}

/*int main()
{
    int n, m;
    cin >> n >> m;
    vector<int> u, v;
    for (int i = 0; i < m; ++i)
    {
        int x, y;
        cin >> x >> y;
        u.push_back(x);
        v.push_back(y);
    }
    cout << find_journey(n, m, u, v) << "\n";
    return 0;
}*/

/*
5 6
0 1
1 0
1 3
3 1
0 4
4 0

3 6
0 1
1 0
1 2
2 1
2 0
0 2
*/

Compilation message (stderr)

islands.cpp: In function 'bool dfs(int)':
islands.cpp:22:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   22 |     for (int i = 0; i < g[x].size(); ++i)
      |                     ~~^~~~~~~~~~~~~
islands.cpp:40:1: warning: control reaches end of non-void function [-Wreturn-type]
   40 | }
      | ^

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