Shallow waters

input/code.cpp: In function 'bool there_is_bfs(std::vector<std::vector<long long int> >&, long long int, long long int, std::vector<long long int>&)':
input/code.cpp:26:33: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<std::vector<long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   26 |         for (long long i = 0; i < adj.size(); ++i)
      |                               ~~^~~~~~~~~~~~

#include <iostream>
#include <vector>
#include <queue>
#include <climits>
#include <algorithm>

using namespace std;


bool there_is_bfs(vector<vector<long long>> &adj, long long s, long long t, vector<long long> &parent)
{
    // No node has been visited yet
    vector<bool> visited(adj.size(), false);

    // Queue for BFS
    queue<long long> q;
    q.push(s);
    visited[s] = true;
    parent[s] = -1;

    // BFS
    while (!q.empty()) {
        long long u = q.front();
        q.pop();

        for (long long i = 0; i < adj.size(); ++i)
        {
            if (!visited[i] and adj[u][i] > 0) {
                if (i == t) {
                    parent[i] = u;
                    return true;
                }
                q.push(i);
                parent[i] = u;
                visited[i] = true;
            }
        }
    }

    // There is no path
    return false;
}


long long ford_fulkerson(vector<vector<long long>> &graph, long long start, long long end)
{
    vector<long long> parent(graph.size());
    vector<long long> max_flows;

    // While there is a path with positive capacities from start to end
    while (there_is_bfs(graph, start, end, parent)) {

        // Calculate path flow for the found path with bfs
        long long path_flow = LLONG_MAX;
        for (long long i = end; i != start; i = parent[i]) {
            long long v = parent[i];
            path_flow = min(path_flow, graph[v][i]);
        }

        // Update max flow
        max_flows.push_back(path_flow);
        //cout << "Found a path with " << path_flow << endl;

        // Update residual capacities
        for (long long i = end; i != start; i = parent[i]) {
            long long v = parent[i];
            graph[v][i] -= path_flow;
            graph[i][v] += path_flow;
        }
    }

    auto m = max_element(max_flows.begin(), max_flows.end());
    return *m;
}

int main() {
    long long n, m;
    cin >> n >> m;

    // Build graph with capacities
    vector<vector<long long>> capacity(n+1, vector<long long>(n+1));

    for (long long i = 1; i < n + 1; ++i) {
        for (long long j = 1; j < n + 1; ++j) {
            long long c;
            cin >> c;
            capacity[i][j] = c;
        }
            
    }

    for (int i = 0; i < m; ++i) {
        vector<vector<long long>> capacity_aux = capacity;
        int start, end;
        cin >> start >> end;
        cout << ford_fulkerson(capacity_aux, start, end) << endl;
    }        
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: WRONG ANSWER

Test 12

Verdict: ACCEPTED

Test 13

Verdict: WRONG ANSWER

Test 14

Verdict: WRONG ANSWER

Test 15

Verdict: WRONG ANSWER

Test 16

Verdict: WRONG ANSWER

Test 17

Verdict: ACCEPTED

Test 18

Verdict: ACCEPTED

Test 19

Verdict: ACCEPTED

Test 20

Verdict: WRONG ANSWER

Test 21

Verdict: ACCEPTED

Test 22

Verdict: WRONG ANSWER

Test 23

Verdict: WRONG ANSWER

Test 24

Verdict: WRONG ANSWER

Test 25

Verdict: WRONG ANSWER

Test 26

Verdict: WRONG ANSWER

Test 27

Verdict: WRONG ANSWER

Test 28

Verdict: WRONG ANSWER

Test 29

Verdict: WRONG ANSWER

Test 30

Verdict: WRONG ANSWER

Test 31

Verdict: WRONG ANSWER

Test 32

Verdict: TIME LIMIT EXCEEDED

Test 33

Verdict: TIME LIMIT EXCEEDED

Test 34

Verdict: TIME LIMIT EXCEEDED

Test 35

Verdict: TIME LIMIT EXCEEDED

Test 36

Verdict: TIME LIMIT EXCEEDED

Test 37

Verdict: TIME LIMIT EXCEEDED

Test 38

Verdict: TIME LIMIT EXCEEDED

Test 39

Verdict: TIME LIMIT EXCEEDED

Test 40

Verdict: TIME LIMIT EXCEEDED

Test 41

Verdict: TIME LIMIT EXCEEDED

Test 42

Verdict: TIME LIMIT EXCEEDED

Test 43

Verdict: TIME LIMIT EXCEEDED

Test 44

Verdict: TIME LIMIT EXCEEDED

Test 45

Verdict: TIME LIMIT EXCEEDED

Test 46

Verdict: TIME LIMIT EXCEEDED

Test 47

Verdict: TIME LIMIT EXCEEDED

Test 48

Verdict: TIME LIMIT EXCEEDED

Test 49

Verdict: TIME LIMIT EXCEEDED

Test 50

Verdict: TIME LIMIT EXCEEDED

Test 51

Verdict: TIME LIMIT EXCEEDED

Test 52

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Test 53

Verdict: TIME LIMIT EXCEEDED

Test 54

Verdict: TIME LIMIT EXCEEDED

Test 55

Verdict: TIME LIMIT EXCEEDED

Test 56

Verdict: TIME LIMIT EXCEEDED

Test 57

Verdict: TIME LIMIT EXCEEDED

Test 58

Verdict: TIME LIMIT EXCEEDED

Test 59

Verdict: TIME LIMIT EXCEEDED

Test 60

Verdict: TIME LIMIT EXCEEDED

Test 61

Verdict: TIME LIMIT EXCEEDED