Submission #1067172

#	Time	Username	Problem	Language	Result	Execution time	Memory
1067172		j_vdd16	Thousands Islands (IOI22_islands)	C++17	9.10 / 100	23 ms	5460 KiB

islands

#include "islands.h"

#include <variant>
#include <algorithm>
#include <bitset>
#include <cstdint>
#include <cstring>
#include <iostream>
#include <limits.h>
#include <math.h>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>

//#define int long long
#define loop(X, N) for(int X = 0; X < (N); X++)
#define all(V) V.begin(), V.end()
#define rall(V) V.rbegin(), V.rend()

using namespace std;

typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int, int> ii;
typedef vector<ii> vii;
typedef vector<vector<ii>> vvii;
typedef vector<bool> vb;
typedef vector<vector<bool>> vvb;

typedef uint64_t u64;
typedef int64_t i64;

int n, m;
vvii adj;

vb vis;
vi depths;

bool success = false;
int counter = 0;
vii inOut;
int dfs(int node, int d, int parent) {
    if (node == parent) return 0;

    if (vis[node]) {
        return 1;
    }
    vis[node] = true;
    depths[node] = d;

    inOut[node].first = counter++;

    int count = 0;
    for (auto [child, idx] : adj[node]) {
        if (child == parent) continue;
        
        int res = dfs(child, d + 1, node);
        count += res;
    }
    if (count >= 2)
        success = true;

    inOut[node].second = counter++;
    return 1;
}

bool isAncestor(int a, int b) {
    return inOut[a].first <= inOut[b].first && inOut[b].first <= inOut[a].second;
}

vi parents;
vi succesPath;
int dfs2(int node, int parent, vi path) {
    if (vis[node]) {
        return 1;
    }
    
    parents[node] = parent;
    vis[node] = true;

    int count = 0;
    vi validIndices;
    for (auto [child, idx] : adj[node]) {
        if (child == parent) continue;
        
        vi childPath = path;
        childPath.push_back(idx);
        int res = dfs2(child, node, path);
        if (res) {
            count += res;
            validIndices.push_back(idx);
        }
    }
    if (count >= 2 && !success) {
        success = true;
        succesPath = path;
        succesPath.push_back(validIndices[0]);
        succesPath.push_back(validIndices[0] ^ 1);
        succesPath.push_back(validIndices[1]);
        succesPath.push_back(validIndices[1] ^ 1);

        for (int i = succesPath.size() - 4 - 1; i >= 0; i++) {
            succesPath.push_back(succesPath[i] ^ 1);
        }
    }

    return 1;
}

std::variant<bool, std::vector<int>> find_journey(int N, int M, vi U, vi V) {
    n = N;
    m = M;
    adj = vvii(n);
    loop(i, m) {
        adj[U[i]].push_back({V[i], i});
    }

    // if (n >= 3) {
    //     int n1 = adj[0][0].first;
    //     int n2 = adj[0][1].first;
    //     return vi{adj[0][0].second, adj[n1][0].second, adj[0][1].second, adj[n2][0].second, adj[n1][0].second, adj[0][0].second, adj[n2][0].second, adj[0][1].second };
    // }

    // return false;

    depths = vi(n);
    counter = 0;
    inOut = vii(n);
    vis = vb(n);
    success = false;
    parents = vi(n);
    dfs2(0, -1, {});

    // vis = vb(n);
    // marked = vi(n);
    // dfs2(0);
    
    if (success) {
        return succesPath;
    }
    return false;

    // return false;

    // return success;
}

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