Submission #714016

#	Time	Username	Problem	Language	Result	Execution time	Memory
714016		t6twotwo	Thousands Islands (IOI22_islands)	C++17	10 / 100	33 ms	4420 KiB

islands

#include "islands.h"
#include <bits/stdc++.h>
using namespace std;
variant<bool, vector<int>> find_journey(int N, int M, vector<int> U, vector<int> V) {
    if (N == 2) {
        vector<int> a, b;
        for (int i = 0; i < M; i++) {
            if (!U[i]) a.push_back(i);
            else b.push_back(i);
        }
        if (a.size() < 2 || b.empty()) return false;
        else return vector<int>{a[0], b[0], a[1], a[0], b[0], a[1]};
    } else if (N <= 400 && M == N * (N - 1)) {
        int x, y, z, t;
        for (int i = 0; i < M; i++) {
            if (U[i] == 0 && V[i] == 1) x = i;
            if (U[i] == 1 && V[i] == 0) y = i;
            if (U[i] == 0 && V[i] == 2) z = i;
            if (U[i] == 2 && V[i] == 0) t = i;
        }
        return vector<int>{x, y, z, t, y, x, t, z};
    } else {
        vector<vector<int>> adj(N);
        for (int i = 0; i < M; i++) {
            adj[U[i]].push_back(V[i]);
        }
        vector<int> vis(N);
        auto dfs = [&](auto dfs, int x, int p) -> bool {
            vis[x] = 1;
            for (int y : adj[x]) {
                if (y == p) continue;
                if (vis[y] == 1) return 1;
                if (!vis[y]) if (dfs(dfs, y, x)) return 1;
            }
            vis[x] = 2;
            return 0;
        };
        return dfs(dfs, 0, - 1);
    }
}

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:21:50: warning: 't' may be used uninitialized in this function [-Wmaybe-uninitialized]
   21 |         return vector<int>{x, y, z, t, y, x, t, z};
      |                                                  ^
islands.cpp:21:50: warning: 'z' may be used uninitialized in this function [-Wmaybe-uninitialized]
islands.cpp:21:50: warning: 'y' may be used uninitialized in this function [-Wmaybe-uninitialized]
islands.cpp:21:50: warning: 'x' may be used uninitialized in this function [-Wmaybe-uninitialized]

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