Cod sursa(job #3154870)

Utilizator matei0000Neacsu Matei matei0000 Data 6 octombrie 2023 17:27:01
Problema Flux maxim Scor 100
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 2.14 kb
#include <bits/stdc++.h>

using namespace std;

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


struct Dinic
{
    struct Edge
    {
        int from, to, cap, ult;
    };

    int n;
    vector<int> dist, last;
    vector<Edge> edges;
    queue<int> q;

    Dinic(int cn)
    {
        n = cn;
        last.assign(n + 1, -1);
    }

    void push(int from, int to, int cap)
    {
        edges.push_back({from, to, cap, last[from]});
        last[from] = edges.size() - 1;

        edges.push_back({to, from, 0, last[to]});
        last[to] = edges.size() - 1;
    }

    bool bfs(int source, int sink)
    {
        dist.assign(n + 1, 1e9);
        q.push(source);
        dist[source] = 0;

        while(!q.empty())
        {
            int x = q.front();
            q.pop();

            for(int y = last[x]; y != -1; y = edges[y].ult)
            {
                if(edges[y].cap > 0 && dist[edges[y].to] == 1e9)
                {
                    dist[edges[y].to] = dist[x] + 1;
                    q.push(edges[y].to);
                }
            }
        }

        return dist[sink] != 1e9;
    }

    int dfs(int source, int sink, int flow)
    {
        if(source == sink)
            return flow;

        int ans = 0;
        for(int y = last[source]; y != -1; y = edges[y].ult)
        {
            if(edges[y].cap > 0 && dist[edges[y].to] == dist[source] + 1)
            {
                int trimis = dfs(edges[y].to, sink, min(flow, edges[y].cap));

                edges[y].cap -= trimis;
                edges[y ^ 1].cap += trimis;

                ans += trimis;
                flow -= trimis;
            }
        }

        return ans;
    }

    int MaxFlow(int source, int sink)
    {
        int ans = 0;
        while(bfs(source, sink))
            ans += dfs(source, sink, 1e9);

        return ans;
    }
};




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

    Dinic d(n);

    for(int i = 0; i < m; i ++)
    {
        int u, v, w;
        in >> u >> v >> w;
        d.push(u, v, w);
    }

    out << d.MaxFlow(1, n);
}