test/dinic.test.cpp

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• Last update: 2024-05-21 00:19:42+09:00
• Problem: https://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=GRL_6_A

Depends on

• data_structure/dinic.hpp

Code

#define PROBLEM "https://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=GRL_6_A"

#include "../data_structure/dinic.hpp"

#include<bits/stdc++.h>
using namespace std;
using ll=long long;




int main() {
    ios::sync_with_stdio(false);
  cin.tie(0);

ll U,V;cin>>U>>V;
Dinic<ll> g(U);

for(ll i=0;i<V;i++) {
  ll u,v,c;cin>>u>>v>>c;
  g.add_edge(u,v,c);
}

cout<<g.max_flow(0,U-1)<<endl;
}

#line 1 "test/dinic.test.cpp"
#define PROBLEM "https://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=GRL_6_A"

#line 2 "data_structure/dinic.hpp"

#include<bits/stdc++.h>
using namespace std;
using ll=long long;


template< typename flow_t >
struct Dinic {
  const flow_t INF;

  struct edge {
    int to;
    flow_t cap;
    int rev;
    bool isrev;
    int idx;
  };

  vector< vector< edge > > graph;
  vector< int > min_cost, iter;

  Dinic(int V) : INF(numeric_limits< flow_t >::max()), graph(V) {}

  void add_edge(int from, int to, flow_t cap, int idx = -1) {
    graph[from].emplace_back((edge) {to, cap, (int) graph[to].size(), false, idx});
    graph[to].emplace_back((edge) {from, 0, (int) graph[from].size() - 1, true, idx});
  }

  bool bfs(int s, int t) {
    min_cost.assign(graph.size(), -1);
    queue< int > que;
    min_cost[s] = 0;
    que.push(s);
    while(!que.empty() && min_cost[t] == -1) {
      int p = que.front();
      que.pop();
      for(auto &e : graph[p]) {
        if(e.cap > 0 && min_cost[e.to] == -1) {
          min_cost[e.to] = min_cost[p] + 1;
          que.push(e.to);
        }
      }
    }
    return min_cost[t] != -1;
  }

  flow_t dfs(int idx, const int t, flow_t flow) {
    if(idx == t) return flow;
    for(int &i = iter[idx]; i < graph[idx].size(); i++) {
      edge &e = graph[idx][i];
      if(e.cap > 0 && min_cost[idx] < min_cost[e.to]) {
        flow_t d = dfs(e.to, t, min(flow, e.cap));
        if(d > 0) {
          e.cap -= d;
          graph[e.to][e.rev].cap += d;
          return d;
        }
      }
    }
    return 0;
  }

  flow_t max_flow(int s, int t) {
    flow_t flow = 0;
    while(bfs(s, t)) {
      iter.assign(graph.size(), 0);
      flow_t f = 0;
      while((f = dfs(s, t, INF)) > 0) flow += f;
    }
    return flow;
  }

  void output() {
    for(int i = 0; i < graph.size(); i++) {
      for(auto &e : graph[i]) {
        if(e.isrev) continue;
        auto &rev_e = graph[e.to][e.rev];
        cout << i << "->" << e.to << " (flow: " << rev_e.cap << "/" << e.cap + rev_e.cap << ")" << endl;
      }
    }
  }
};
#line 4 "test/dinic.test.cpp"

#line 6 "test/dinic.test.cpp"
using namespace std;
using ll=long long;




int main() {
    ios::sync_with_stdio(false);
  cin.tie(0);

ll U,V;cin>>U>>V;
Dinic<ll> g(U);

for(ll i=0;i<V;i++) {
  ll u,v,c;cin>>u>>v>>c;
  g.add_edge(u,v,c);
}

cout<<g.max_flow(0,U-1)<<endl;
}

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