Cod sursa(job #2903110)

Utilizator tibinyteCozma Tiberiu-Stefan tibinyte Data 17 mai 2022 09:51:49
Problema Flux maxim Scor 100
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 2.46 kb
#include <bits/stdc++.h>
using namespace std;
ifstream fin("maxflow.in");
ofstream fout("maxflow.out");
struct edge
{
    int a, b, flow, cap;
};
struct Dinic
{
    vector<edge> edges;
    vector<vector<int>> g;
    vector<int> level, next;
    int s, t;
    void add_edge(int a, int b, int cap)
    {
        int m = edges.size();
        edges.push_back({a, b, 0, cap});
        edges.push_back({b, a, 0, 0});
        g[a].push_back(m);
        g[b].push_back(m + 1);
    }
    void build(int n, int _s, int _t)
    {
        g.resize(n + 1), level.resize(n + 1), next.resize(n + 1);
        s = _s;
        t = _t;
    }
    bool bfs()
    {
        queue<int> q;
        level[s] = 0;
        q.push(s);
        while (!q.empty())
        {
            int node = q.front();
            q.pop();
            for (auto i : g[node])
            {
                edge x = edges[i];
                if (x.cap - x.flow < 1 || level[x.b] != -1)
                {
                    continue;
                }
                level[x.b] = level[node] + 1;
                q.push(x.b);
            }
        }
        return level[t] != -1;
    }
    int dfs(int node, int push)
    {
        if (node == t || push == 0)
        {
            return push;
        }
        for (int &i = next[node]; i < g[node].size(); ++i)
        {
            edge x = edges[g[node][i]];
            if (x.cap - x.flow < 1 || level[x.b] != level[node] + 1)
            {
                continue;
            }
            int flow = dfs(x.b, min(push, x.cap - x.flow));
            if (flow == 0)
            {
                continue;
            }
            edges[g[node][i]].cap -= flow;
            edges[g[node][i] ^ 1].cap += flow;
            return flow;
        }
        return 0;
    }
    int flow()
    {
        int ans = 0;
        while (true)
        {
            fill(level.begin(), level.end(), -1);
            if (!bfs())
            {
                break;
            }
            fill(next.begin(),next.end(),0);
            while(int add = dfs(s,INT_MAX)){
                ans+=add;
            }
        }
        return ans;
    }
};
int32_t main()
{
    cin.tie(nullptr)->sync_with_stdio(false);
    int n,m;
    fin>>n>>m;
    Dinic G;
    G.build(n,1,n);
    for(int i= 1; i <= m ; ++i){
        int a, b, cap;
        fin>>a>>b>>cap;
        G.add_edge(a,b,cap);
    }
    fout<<G.flow();
}