Cod sursa(job #2870912)

Utilizator Cosmin2004_InfoMoldoveanu Cosmin Cosmin2004_Info Data 12 martie 2022 17:34:11
Problema Flux maxim Scor 100
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 2.01 kb
#include <bits/stdc++.h>

using namespace std;
#ifndef HOME
ifstream fin("maxflow.in");
ofstream fout("maxflow.out");
#else
ifstream fin("ciorna.in");
ofstream fout("ciorna.out");
#endif
using ll = long long;
class Flow {
    const int max_flow = 1e9;
    struct Edge { int from, to, cap; };
    int n, k, s, t;
    vector <Edge> e;
    vector <vector <int>> g;
    vector <int> lvl, rem;
public:
    Flow(int n) : n(n), k(0), s(1), t(n), e(0), g(n + 1), lvl(n + 1, 0), rem(n + 1, 0) {}
    void add_edge(int u, int v, int w) {
        g[u].push_back(k++);
        g[v].push_back(k++);
        e.push_back({u, v, w});
        e.push_back({v, u, 0});
    }
    inline bool bfs() {
        fill(lvl.begin(), lvl.end(), 0);
        queue <int> q;
        for(lvl[s] = 1, q.push(s); !q.empty(); q.pop()) {
            int u = q.front();
            for(int id : g[u]) {
                int v = e[id].to;
                if(!lvl[v] && e[id].cap) {
                    lvl[v] = lvl[u] + 1;
                    q.push(v);
                }
            }
        }

        return lvl[t];
    }
    int dfs(int u, int flow) {
        if(u == t || !flow) return flow;
        for(int& cid = rem[u]; cid < g[u].size(); cid++) {
            int id = g[u][cid], v = e[id].to;
            if(!e[id].cap || lvl[v] != lvl[u] + 1) continue;
            int f = dfs(v, min(flow, e[id].cap));
            if(!f) continue;
            e[id].cap -= f;
            e[id ^ 1].cap += f;
            return f;
        }
        return 0;
    }
    ll dinic(int ss, int tt) {
        s = ss; t = tt;
        ll flow = 0;
        while(bfs()) {
            fill(rem.begin(), rem.end(), 0);
            while(int f = dfs(s, max_flow))
                flow += f;
        }
        return flow;
    }
};

int main()
{
    int n, m, u, v, w;
    fin >> n >> m;
    Flow F(n);
    for(int i = 1; i <= m; i++)
        fin >> u >> v >> w,
        F.add_edge(u, v, w);
    fout << F.dinic(1, n);
    return 0;
}