:heavy_check_mark: verify/flow/AOJ_GRL_6_A.test.cpp

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Code

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

#include "template/template.hpp"
#include "flow/max-flow.hpp"

int main() {
  int n, m;
  in(n, m);
  MaxFlow<int> g(n);
  rep(i, 0, m) {
    int u, v, w;
    in(u, v, w);
    g.add_edge(u, v, w);
  }
  out(g.flow(0, n - 1));
}
#line 1 "verify/flow/AOJ_GRL_6_A.test.cpp"
#define PROBLEM "https://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=GRL_6_A"

#line 2 "template/template.hpp"
#include <bits/stdc++.h>
using namespace std;

#line 2 "template/macro.hpp"
#define rep(i, a, b) for (int i = (a); i < (int)(b); i++)
#define rrep(i, a, b) for (int i = (int)(b) - 1; i >= (a); i--)
#define ALL(v) (v).begin(), (v).end()
#define UNIQUE(v) sort(ALL(v)), (v).erase(unique(ALL(v)), (v).end())
#define SZ(v) (int)v.size()
#define MIN(v) *min_element(ALL(v))
#define MAX(v) *max_element(ALL(v))
#define LB(v, x) int(lower_bound(ALL(v), (x)) - (v).begin())
#define UB(v, x) int(upper_bound(ALL(v), (x)) - (v).begin())
#define YN(b) cout << ((b) ? "YES" : "NO") << "\n";
#define Yn(b) cout << ((b) ? "Yes" : "No") << "\n";
#define yn(b) cout << ((b) ? "yes" : "no") << "\n";
#line 6 "template/template.hpp"

#line 2 "template/util.hpp"
using uint = unsigned int;
using ll = long long int;
using ull = unsigned long long;
using i128 = __int128_t;
using u128 = __uint128_t;

template <class T, class S = T>
S SUM(const vector<T> &a) {
  return accumulate(ALL(a), S(0));
}
template <class T>
inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T>
inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}

template <class T>
int popcnt(T x) {
  return __builtin_popcountll(x);
}
template <class T>
int topbit(T x) {
  return (x == 0 ? -1 : 63 - __builtin_clzll(x));
}
template <class T>
int lowbit(T x) {
  return (x == 0 ? -1 : __builtin_ctzll(x));
}
#line 8 "template/template.hpp"

#line 2 "template/inout.hpp"
struct Fast {
  Fast() {
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);
    cout << fixed << setprecision(15);
  }
} fast;

template <class T1, class T2>
istream &operator>>(istream &is, pair<T1, T2> &p) {
  return is >> p.first >> p.second;
}
template <class T1, class T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) {
  return os << p.first << " " << p.second;
}
template <class T>
istream &operator>>(istream &is, vector<T> &a) {
  for (auto &v : a) is >> v;
  return is;
}
template <class T>
ostream &operator<<(ostream &os, const vector<T> &a) {
  for (auto it = a.begin(); it != a.end();) {
    os << *it;
    if (++it != a.end()) os << " ";
  }
  return os;
}
template <class T>
ostream &operator<<(ostream &os, const set<T> &st) {
  os << "{";
  for (auto it = st.begin(); it != st.end();) {
    os << *it;
    if (++it != st.end()) os << ",";
  }
  os << "}";
  return os;
}
template <class T1, class T2>
ostream &operator<<(ostream &os, const map<T1, T2> &mp) {
  os << "{";
  for (auto it = mp.begin(); it != mp.end();) {
    os << it->first << ":" << it->second;
    if (++it != mp.end()) os << ",";
  }
  os << "}";
  return os;
}

void in() {}
template <typename T, class... U>
void in(T &t, U &...u) {
  cin >> t;
  in(u...);
}
void out() { cout << "\n"; }
template <typename T, class... U, char sep = ' '>
void out(const T &t, const U &...u) {
  cout << t;
  if (sizeof...(u)) cout << sep;
  out(u...);
}
#line 10 "template/template.hpp"

#line 2 "template/debug.hpp"
#ifdef LOCAL
#define debug 1
#define show(...) _show(0, #__VA_ARGS__, __VA_ARGS__)
#else
#define debug 0
#define show(...) true
#endif
template <class T>
void _show(int i, T name) {
  cerr << '\n';
}
template <class T1, class T2, class... T3>
void _show(int i, const T1 &a, const T2 &b, const T3 &...c) {
  for (; a[i] != ',' && a[i] != '\0'; i++) cerr << a[i];
  cerr << ":" << b << " ";
  _show(i + 1, a, c...);
}
#line 2 "flow/max-flow.hpp"

#line 2 "data-structure/simple-queue.hpp"

template <class T>
struct SimpleQueue {
 private:
  vector<T> a;
  int p;

 public:
  SimpleQueue() {}
  SimpleQueue(int n) { a.reserve(n); }
  void reserve(int n) { a.reserve(n); }
  int size() { return a.size() - p; }
  bool empty() { return a.size() == p; }
  void push(const T& v) { a.push_back(v); }
  T& front() { return a[p]; }
  void pop() { p++; }
  void clear() {
    a.clear();
    p = 0;
  }
};
#line 4 "flow/max-flow.hpp"

template <class Cap = long long>
struct MaxFlow {
 public:
  MaxFlow() : _n(0) {}
  explicit MaxFlow(int n) : _n(n), g(n) {}

  int add_edge(int from, int to, Cap cap) {
    assert(0 <= from && from < _n);
    assert(0 <= to && to < _n);
    assert(0 <= cap);
    int m = int(pos.size());
    pos.push_back({from, int(g[from].size())});
    int from_id = int(g[from].size());
    int to_id = int(g[to].size());
    if (from == to) to_id++;
    g[from].push_back(_edge{to, to_id, cap});
    g[to].push_back(_edge{from, from_id, 0});
    return m;
  }

  struct edge {
    int from, to;
    Cap cap, flow;
  };

  edge get_edge(int i) {
    int m = int(pos.size());
    assert(0 <= i && i < m);
    auto _e = g[pos[i].first][pos[i].second];
    auto _re = g[_e.to][_e.rev];
    return edge{pos[i].first, _e.to, _e.cap + _re.cap, _re.cap};
  }
  vector<edge> edges() {
    int m = int(pos.size());
    vector<edge> result;
    for (int i = 0; i < m; i++) {
      result.push_back(get_edge(i));
    }
    return result;
  }
  void change_edge(int i, Cap new_cap, Cap new_flow) {
    int m = int(pos.size());
    assert(0 <= i && i < m);
    assert(0 <= new_flow && new_flow <= new_cap);
    auto& _e = g[pos[i].first][pos[i].second];
    auto& _re = g[_e.to][_e.rev];
    _e.cap = new_cap - new_flow;
    _re.cap = new_flow;
  }

  Cap flow(int s, int t) {
    return flow(s, t, numeric_limits<Cap>::max());
  }
  Cap flow(int s, int t, Cap flow_limit) {
    assert(0 <= s && s < _n);
    assert(0 <= t && t < _n);
    assert(s != t);

    vector<int> level(_n), iter(_n);
    SimpleQueue<int> que;

    auto bfs = [&]() {
      fill(level.begin(), level.end(), -1);
      level[s] = 0;
      que.clear();
      que.push(s);
      while (!que.empty()) {
        int v = que.front();
        que.pop();
        for (auto& e : g[v]) {
          if (e.cap == 0 || level[e.to] >= 0) continue;
          level[e.to] = level[v] + 1;
          if (e.to == t) return;
          que.push(e.to);
        }
      }
    };
    auto dfs = [&](auto self, int v, Cap up) {
      if (v == s) return up;
      Cap res = 0;
      int level_v = level[v];
      for (int& i = iter[v]; i < int(g[v].size()); i++) {
        _edge& e = g[v][i];
        if (level_v <= level[e.to] || g[e.to][e.rev].cap == 0) continue;
        Cap d = self(self, e.to, min(up - res, g[e.to][e.rev].cap));
        if (d <= 0) continue;
        g[v][i].cap += d;
        g[e.to][e.rev].cap -= d;
        res += d;
        if (res == up) return res;
      }
      level[v] = _n;
      return res;
    };

    Cap flow = 0;
    while (flow < flow_limit) {
      bfs();
      if (level[t] == -1) break;
      fill(iter.begin(), iter.end(), 0);
      Cap f = dfs(dfs, t, flow_limit - flow);
      if (!f) break;
      flow += f;
    }
    return flow;
  }

  vector<bool> min_cut(int s) {
    vector<bool> visited(_n);
    SimpleQueue<int> que;
    que.push(s);
    while (!que.empty()) {
      int p = que.front();
      que.pop();
      visited[p] = true;
      for (auto& e : g[p]) {
        if (e.cap && !visited[e.to]) {
          visited[e.to] = true;
          que.push(e.to);
        }
      }
    }
    return visited;
  }

 private:
  int _n;
  struct _edge {
    int to, rev;
    Cap cap;
  };
  vector<pair<int, int>> pos;
  vector<vector<_edge>> g;
};

/**
 * @brief Max Flow
 * @docs docs/flow/max-flow.md
 */
#line 5 "verify/flow/AOJ_GRL_6_A.test.cpp"

int main() {
  int n, m;
  in(n, m);
  MaxFlow<int> g(n);
  rep(i, 0, m) {
    int u, v, w;
    in(u, v, w);
    g.add_edge(u, v, w);
  }
  out(g.flow(0, n - 1));
}
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