Submission #1173663

#	Time	Username	Problem	Language	Result	Execution time	Memory
1173663		SpyrosAliv	Thousands Islands (IOI22_islands)	C++20	10 / 100	22 ms	7140 KiB

islands

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

int n, m;
vector<int> u, v;
vector<vector<int>> av;
bool cycle;
vector<bool> vis;

void dfs(int node, int par) {
    if (cycle) return;
    vis[node] = true;
    vector<int> targs;
    for (int i = 1; i < (int)av[node].size(); i++) {
        targs.push_back(v[av[node][i]]);
    }
    sort(targs.begin(), targs.end());
    int s = targs.size();
    for (int i = 1; i < s; i++) {
        if (targs[i] == targs[i-1]) {
            cycle = true;
            return;
        }
    }
    for (int i = 0; i < s; i++) {
        if (targs[i] == par) continue;
        if (vis[targs[i]]) {
            cycle = true;
            return;
        }
    }
    for (int i = 0; i < s; i++) {
        if (targs[i] != par) {
            dfs(targs[i], node);
            if (cycle) return;
        }
    }
}

variant<bool, vector<int>> find_journey(int N, int M, vector<int> U, vector<int> V) {
    // tree -> impossible
    n = N;
    m = M;
    u = U;
    v = V;
    av.clear();
    av.resize(n);
    vis.assign(n, false);
    for (int i = 0; i < m; i++) {
        av[u[i]].push_back(i);
    }
    cycle = false;
    dfs(0, -1);
    if (n == 2) {
        int cnt1 = 0, cnt2 = 0;
        vector<int> a, b;
        for (int i = 0; i < m; i++) {
            if (u[i] == 0) {
                cnt1++;
                a.push_back(i);
            }
            else {
                cnt2++;
                b.push_back(i);
            }
        }
        if (cnt1 < 2 || cnt2 < 1) return false;
        vector<int> ans = {a[0], b[0], a[1], a[0], b[0], a[1]};
        return ans;
    }
    else {
        vector<int> goB, goC, b, c;
        for (int i = 0; i < m; i++) {
            if (u[i] == 0) {
                if (v[i] == 1) goB.push_back(i);
                else if (v[i] == 2) goC.push_back(i);
            }
            else if (u[i] == 1 && v[i] == 0) b.push_back(i);
            else if (u[i] == 2 && v[i] == 0) c.push_back(i);
        }
        if (goB.size() && goC.size() && b.size() && c.size()) {
            vector<int> ans = {goB[0], b[0], goC[0], c[0], b[0], goB[0], c[0], goC[0]};
            return ans;
        }
    }
    if (!cycle) return false;
    else return true;
}

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