Submission #706529

#	Time	Username	Problem	Language	Result	Execution time	Memory
706529		danikoynov	Thousands Islands (IOI22_islands)	C++17	35 / 100	170 ms	22988 KiB

islands

#include "islands.h"

#include <variant>
#include <vector>
#include <queue>
#include <iostream>
using namespace std;

const int maxn = 1e5 + 10;
int seen[maxn], in_deg[maxn], out_deg[maxn];
int n, m;
vector < int > links[maxn], rev_links[maxn];
vector < pair < int, int > > graph[maxn];
vector < int > path[3];

int clear_useless()
{
    queue < int > q;
    for (int i = 0; i < n; i ++)
    {
        if (!out_deg[i])
            q.push(i);
    }

    int start = 0;
    while(!q.empty() || out_deg[start] <= 1)
    {
        if (!q.empty())
        {
            int node = q.front();
            q.pop();
            seen[node] = -1;
            for (int dest : rev_links[node])
            {
                out_deg[dest] --;
                if (out_deg[dest] == 0)
                    q.push(dest);
            }
        }
        while(out_deg[start] <= 1)
        {
            seen[start] = -1;
            out_deg[start] = 0;
            for (int dest : rev_links[start])
            {
                out_deg[dest] --;
                if (out_deg[dest] == 0)
                    q.push(dest);
            }

            pair < int, int > nxt = make_pair(-1, 0);
            for (pair < int, int > cur : graph[start])
            {
                if (seen[cur.first] != -1)
                {
                    nxt = cur;
                    break;
                }
            }

            if (nxt.first == -1)
                return -1;
            start = nxt.first;
            path[2].push_back(nxt.second);
        }
    }

    return start;
}

std::variant<bool, std::vector<int>> find_journey(int N, int M, std::vector<int> U, std::vector<int> V)
{
    n = N;
    m = M;
    for (int i = 0; i < M; i ++)
    {
        links[U[i]].push_back(V[i]);
        rev_links[V[i]].push_back(U[i]);
        in_deg[V[i]] ++;
        out_deg[U[i]] ++;

        graph[U[i]].push_back({V[i], i});
    }

    int root = clear_useless();
    if (root < 0)
        return false;
    ///cout << " root " << root << endl;
    ///dfs(start, 0, start);
    return true;
}

• Subtask 1: 1.75 / 5
• Subtask 2: 1.75 / 5
• Subtask 3: 7.35 / 21
• Subtask 4: 8.399999999999999 / 24
• Subtask 5: 15.749999999999998 / 45