BFS
(graph/bfs.hpp)

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• Last update: 2021-08-01 23:46:19+09:00
• Include: #include "graph/bfs.hpp"

Depends on

• graph/template.hpp

Verified with

• test/aoj/ALDS_1_11_C.bfs.test.cpp

Code

#ifndef __GRAPH__BFS
#define __GRAPH__BFS

// @title BFS
#include "template.hpp"

#include <algorithm>
#include <functional>
#include <limits>
#include <queue>
#include <utility>
#include <vector>

template < typename T >
struct BFS {
  using P = std::pair<T, int>; // <始点からの距離, 点のid>
  const T INF; // 十分に大きいがoverflowしない値として、型Tの最大値の半分を使う
  const int V; // 頂点数
  Graph<T> g;
  std::vector<T> dist; // 始点からの距離
  std::vector<bool> visit; // すでに探索済みの点か
  BFS(Graph<T> &g): INF(std::numeric_limits<T>::max()/2), V(g.size()), g(g), dist(V), visit(V) {}
  BFS(Graph<T> &g, int V): INF(std::numeric_limits<T>::max()/2), V(V), g(g), dist(V), visit(V) {}
  void init(int s) {
    std::fill(dist.begin(), dist.end(), INF);
    std::fill(visit.begin(), visit.end(), false);
    dist[s] = T(); // 始点の距離を0で初期化
    std::queue<P> q;
    q.push({dist[s], s});
    while (!q.empty()) {
      P node = q.front(); q.pop();
      int from = node.second;
      if (visit[from]) continue;
      visit[from] = true;
      for (auto &e : g[from]) {
        if (visit[e.to]) continue;
        T d = node.first + e.cost;
        if (d >= dist[e.to]) continue;
        q.push({d, e.to});
        dist[e.to] = d;
      }
    }
  }
};

#endif // __GRAPH__BFS

#line 1 "graph/bfs.hpp"



// @title BFS
#line 1 "graph/template.hpp"



#include <iostream>
#include <vector>

template< typename T >
struct Edge {
  int from, to;
  T cost;
  Edge() {}
  Edge(int f, int t) : from(f), to(t), cost(1) {}
  Edge(int f, int t, T c) : from(f), to(t), cost(c) {}
  friend bool operator < (const Edge& lhs, const Edge& rhs) { return lhs.cost < rhs.cost; };
  friend bool operator > (const Edge& lhs, const Edge& rhs) { return rhs < lhs; };
  friend bool operator <= (const Edge& lhs, const Edge& rhs) { return !(lhs > rhs); };
  friend bool operator >= (const Edge& lhs, const Edge& rhs) { return !(lhs < rhs); };
};

template< typename T >
using Edges = std::vector< Edge< T > >;
template< typename T >
using Graph = std::vector< Edges< T > >;

template< typename T >
void debug(Graph<T> &g, int n = -1) {
    if (n == -1) n = g.size();
    for (int i = 0; i < n; ++i) {
        std::cerr << i  << "\t";
        for (auto &e: g[i]) {
            std::cerr << e.to << ",";
        }
        std::cerr << std::endl;
    }
}


#line 6 "graph/bfs.hpp"

#include <algorithm>
#include <functional>
#include <limits>
#include <queue>
#include <utility>
#line 13 "graph/bfs.hpp"

template < typename T >
struct BFS {
  using P = std::pair<T, int>; // <始点からの距離, 点のid>
  const T INF; // 十分に大きいがoverflowしない値として、型Tの最大値の半分を使う
  const int V; // 頂点数
  Graph<T> g;
  std::vector<T> dist; // 始点からの距離
  std::vector<bool> visit; // すでに探索済みの点か
  BFS(Graph<T> &g): INF(std::numeric_limits<T>::max()/2), V(g.size()), g(g), dist(V), visit(V) {}
  BFS(Graph<T> &g, int V): INF(std::numeric_limits<T>::max()/2), V(V), g(g), dist(V), visit(V) {}
  void init(int s) {
    std::fill(dist.begin(), dist.end(), INF);
    std::fill(visit.begin(), visit.end(), false);
    dist[s] = T(); // 始点の距離を0で初期化
    std::queue<P> q;
    q.push({dist[s], s});
    while (!q.empty()) {
      P node = q.front(); q.pop();
      int from = node.second;
      if (visit[from]) continue;
      visit[from] = true;
      for (auto &e : g[from]) {
        if (visit[e.to]) continue;
        T d = node.first + e.cost;
        if (d >= dist[e.to]) continue;
        q.push({d, e.to});
        dist[e.to] = d;
      }
    }
  }
};

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