Submission #67727

#	Time	Username	Problem	Language	Result	Execution time	Memory
67727		aquablitz11	Toy Train (IOI17_train)	C++14	23 / 100	940 ms	1820 KiB

train

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

const int N = 5e3+10;
vector<int> G[N], R[N];

vector<int> who_wins(vector<int> A, vector<int> C, vector<int> U, vector<int> V)
{
    // input
    int n = A.size();
    int m = U.size();
    for (int i = 0; i < m; ++i) {
        G[U[i]].push_back(V[i]);
        R[V[i]].push_back(U[i]);
    }

    vector<int> ans(n, 0);
    for (int i = 0; i < n; ++i) if (C[i]) { // i = main recharger we need for cycle
        // first step: find all nodes that can be forced to reach i
        vector<bool> reach(n, false);
        vector<int> cnt(n, 0);
        queue<int> Q;
        Q.push(i);
        reach[i] = true;
        while (!Q.empty()) {
            int u = Q.front(); Q.pop();
            for (auto p : R[u]) if (!reach[p]) {
                ++cnt[p];
                if ((A[p] && cnt[p] == 1) || (!A[p] && cnt[p] == G[p].size())) {
                    reach[p] = true;
                    Q.push(p);
                }
            }
        }
        // second step: find all nodes that are part of i-cycle
        vector<bool> cycle(n, false);
        fill(cnt.begin(), cnt.end(), 0); // use as vis array
        Q.push(i);
        cnt[i] = 1;
        while (!Q.empty()) {
            int u = Q.front(); Q.pop();
            int cntr = 0;
            for (auto v : G[u]) if (reach[v]) ++cntr;
            if ((A[u] && cntr > 0) || (!A[u] && cntr == G[u].size())) {
                cycle[u] = true;
                for (auto v : G[u]) if (!cnt[v]) {
                    cnt[v] = 1;
                    Q.push(v);
                }
            }
        }
        // third step: find all nodes that could reach the cycle
        fill(cnt.begin(), cnt.end(), 0);
        for (int u = 0; u < n; ++u) if (cycle[u])
            Q.push(u);
        while (!Q.empty()) {
            int u = Q.front(); Q.pop();
            ans[u] = true;
            for (auto p : R[u]) if (!cycle[p]) {
                ++cnt[p];
                if ((A[p] && cnt[p] == 1) || (!A[p] && cnt[p] == G[p].size())) {
                    cycle[p] = true;
                    Q.push(p);
                }
            }
        }
    }

    return ans;
}

Compilation message (stderr)

train.cpp: In function 'std::vector<int> who_wins(std::vector<int>, std::vector<int>, std::vector<int>, std::vector<int>)':
train.cpp:30:63: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
                 if ((A[p] && cnt[p] == 1) || (!A[p] && cnt[p] == G[p].size())) {
train.cpp:45:54: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             if ((A[u] && cntr > 0) || (!A[u] && cntr == G[u].size())) {
                                                 ~~~~~^~~~~~~~~~~~~~
train.cpp:62:63: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
                 if ((A[p] && cnt[p] == 1) || (!A[p] && cnt[p] == G[p].size())) {

• Subtask 1: 0 / 5
• Subtask 2: 0 / 10
• Subtask 3: 11 / 11
• Subtask 4: 0 / 11
• Subtask 5: 12 / 12
• Subtask 6: 0 / 51