Edmon Karp's algorithm [maxFlow]

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

#define INF 1e9

int res[40][40], f, s, t;
vector<int> parent;

void augment(int v, int bottleNeck){

    if(v == s){ // found start node
        f = bottleNeck; return ;
    }

    if(parent[v] != -1){
        augment(parent[v], min(bottleNeck, res[parent[v]][v])); // reverse to start node by parent
        res[parent[v]][v] -= f;
        res[v][parent[v]] += f;
    }
}


int main(){
    int n; scanf("%d %d %d", &n, &s, &t);

    for(int i=0; i<n; ++i){
        int m; scanf("%d", &m);

        for(int j=0; j<m; ++j){
            int v, w; scanf("%d %d", &v, &w);
            res[i][v] = w;
        }
    }

    int mf = 0;
    while(1){
        f = 0;
        vector<int> dist(40, INF);
        dist[s] = 0;
        parent.assign(40, -1);

        queue<int> q; q.push(s);
        while(!q.empty()){ // breadth first search
            int u = q.front(); q.pop();

            if(u == t) break;
            for(int v=0; v < 40; v++){
                if(res[u][v] > 0 && dist[v] == INF){
                    dist[v] = dist[u] + 1;
                    q.push(v);
                    parent[v] = u; // set parent for every node
                }
            }
        }
        augment(t, INF); // maximize flow
        if(f == 0) break;
        mf += f;
    }

    printf("%d", mf);
    return 0;
}