Cod sursa(job #2961277)

Utilizator witekIani Ispas witek Data 6 ianuarie 2023 02:54:22
Problema Flux maxim Scor 70
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 1.64 kb
#include <iostream>
#include <fstream>
#include <vector>
#include <queue>
using namespace std;

ifstream fin("maxflow.in");
ofstream fout("maxflow.out");

int n, m;
vector <vector<int>> v, c;
vector <int> t;
vector <bool> visited;

void init() {
    v = vector <vector<int>> (n + 1);
    c = vector <vector<int>> (n + 1, vector <int> (n + 1));
    t = vector <int> (n + 1);
    visited = vector <bool> (n + 1);
}

void read() {
    fin >> n >> m;
    init();
    int x, y, cap;
    for(int i = 1; i <= m; i ++) {
        fin >> x >> y >> cap;
        v[x].push_back(y);
        v[y].push_back(x);
        c[x][y] = cap;
    }
}

bool bfs() {
    queue <int> q;
    fill(visited.begin(), visited.end(), 0);
    q.push(1);
    visited[1] = true;
    t[1] = -1;
    int node;
    while(!q.empty()) {
        node = q.front();
        q.pop();
        for(const auto& neighbour : v[node]) {
            if(!visited[neighbour] && c[node][neighbour]) {
                t[neighbour] = node;
                if (neighbour == n)
                    return true;
                visited[neighbour] = true;
                q.push(neighbour);
            }
        }
    }
    return false;
}

int getMaxFlow() {
    int ansFlow = 0;
    while(bfs()) {
        int minFlow = 2e9;
        for (int node = n; node != 1; node = t[node]) {
            if (c[t[node]][node] < minFlow)
                minFlow = c[t[node]][node];
        }
        ansFlow += minFlow;
        for (int node = n; node != 1; node = t[node]) {
            c[t[node]][node] -= minFlow;
            c[node][t[node]] += minFlow;
        }
    }
    return ansFlow;
}


int main() {
    read();
    fout << getMaxFlow();
}