test/aoj/GRL_6_A.ford_fulkerson.test.cpp

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• Last update: 2024-01-08 01:32:22+09:00
• Problem: http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=GRL_6_A

Depends on

• Ford-Fulkerson Algorithm (flow/ford_fulkerson.hpp)

Code

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

#include <bits/stdc++.h>

#include "../../flow/ford_fulkerson.hpp"
using namespace std;

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

    int V, E;
    cin >> V >> E;
    FordFulkerson<int> flow(V);
    for (int i = 0; i < E; i++) {
        int u, v, c;
        cin >> u >> v >> c;
        flow.add_edge(u, v, c);
    }
    cout << flow.max_flow(0, V - 1) << endl;
}

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

#include <bits/stdc++.h>

#line 7 "flow/ford_fulkerson.hpp"

template <typename T>
class FordFulkerson {
   public:
    FordFulkerson() = default;
    explicit FordFulkerson(int n) : G(n), used(n) {}

    void add_edge(int u, int v, T cap) {
        G[u].push_back({v, (int)G[v].size(), cap});
        G[v].push_back({u, (int)G[u].size() - 1, 0});
    }

    T max_flow(int s, int t) {
        T flow = 0;
        while (true) {
            std::fill(used.begin(), used.end(), false);
            T f = dfs(s, t, INF);
            if (f == 0) return flow;
            flow += f;
        }
    }

    std::set<int> min_cut(int s) {
        std::stack<int> st;
        std::set<int> visited;
        st.push(s);
        visited.insert(s);
        while (!st.empty()) {
            int v = st.top();
            st.pop();
            for (auto& e : G[v]) {
                if (e.cap > 0 && !visited.count(e.to)) {
                    visited.insert(e.to);
                    st.push(e.to);
                }
            }
        }
        return visited;
    }

   private:
    struct Edge {
        int to, rev;
        T cap;
    };

    const T INF = std::numeric_limits<T>::max() / 2;

    std::vector<std::vector<Edge>> G;
    std::vector<bool> used;

    T dfs(int v, int t, T f) {
        if (v == t) return f;
        used[v] = true;
        for (auto& e : G[v]) {
            if (!used[e.to] && e.cap > 0) {
                T d = dfs(e.to, t, std::min(f, e.cap));
                if (d > 0) {
                    e.cap -= d;
                    G[e.to][e.rev].cap += d;
                    return d;
                }
            }
        }
        return 0;
    }
};
#line 7 "test/aoj/GRL_6_A.ford_fulkerson.test.cpp"
using namespace std;

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

    int V, E;
    cin >> V >> E;
    FordFulkerson<int> flow(V);
    for (int i = 0; i < E; i++) {
        int u, v, c;
        cin >> u >> v >> c;
        flow.add_edge(u, v, c);
    }
    cout << flow.max_flow(0, V - 1) << endl;
}

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