Cod sursa(job #3231096)

Utilizator adiadi11Adrian Ariton adiadi11 Data 24 mai 2024 19:29:11
Problema Flux maxim Scor 0
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 1.92 kb
#include <iostream>
#include <vector>
#include <set>
#include <queue>
#include <cmath>
#include <algorithm>
using namespace std;
struct Edge {
    int from;
    int to;
    int cap;
    int flow;
    Edge *back;

    Edge(int f, int t, int c, int ff, Edge *b) : from(f), to(t), cap(c), flow(ff), back(b) {}
};

pair<int, vector<Edge *> > bfs(vector<vector<Edge *> > edges, int n) {
    vector<int> vis(n+1, 0);
    vector<Edge *> predec(n+1, 0);
    queue<int> q;
    predec[1] = nullptr;
    q.push(1);
    while(!q.empty()) {
        int nod = q.front();
        vis[nod] = 1;
        if (nod == n)
            break;
        q.pop();
        for (Edge *edge : edges[nod]) {
            int neigh = edge->to;
            int cap = edge->cap;
            int flow = edge->flow;
            if (!(flow == cap || vis[neigh])) {
                q.push(neigh);
                predec[neigh] = edge;
            } 
        }
    }

    return make_pair(vis[n], predec);
}

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

    vector<vector<Edge *> > edges(n+1);

    for (int i = 0; i  < m; ++i) {
        int x, y, c;
        cin >> x >> y >> c;
        Edge* ed = new Edge(x, y, c, 0, nullptr);
        Edge* rev = new Edge(y, x, 0, 0, ed);
        ed->back = rev;
        edges[x].push_back(ed);
        edges[y].push_back(rev);
    }
    long long deff = 0;
    while(true) {
        auto pg = bfs(edges, n);
        auto ok = pg.first;
        auto predec = pg.second;
        if (!ok)
            break;
        int flow = 1000001;
        for (Edge* edge = predec[n]; edge != nullptr; edge = predec[edge->from]) {
            flow = min (flow, edge->cap - edge->flow);
        }

        if (flow == 0)
            break;

        for (Edge* edge = predec[n]; edge != nullptr; edge = predec[edge->from]) {
            edge->flow = edge->flow + flow;
            edge->back->flow =  edge->back->flow - flow;
        }

        deff += flow;
    }

    cout << deff;



}