C++ Library for Competitive Programming
#include "emthrm/graph/enumerate_bridges.hpp"
$O(\lvert V \rvert + \lvert E \rvert)$
名前 | 戻り値 |
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template <typename CostType> std::vector<Edge<CostType>> enumerate_bridges(const std::vector<std::vector<Edge<CostType>>>& graph);
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無向グラフ $\mathrm{graph}$ の橋 |
https://onlinejudge.u-aizu.ac.jp/solutions/problem/GRL_3_B/review/4082847/emthrm/C++14
#ifndef EMTHRM_GRAPH_ENUMERATE_BRIDGES_HPP_
#define EMTHRM_GRAPH_ENUMERATE_BRIDGES_HPP_
#include <algorithm>
#include <vector>
#include "emthrm/graph/edge.hpp"
namespace emthrm {
template <typename CostType>
std::vector<Edge<CostType>> enumerate_bridges(
const std::vector<std::vector<Edge<CostType>>>& graph) {
const int n = graph.size();
std::vector<Edge<CostType>> res;
std::vector<int> depth(n, -1), imos(n, 0);
const auto dfs = [&graph, &res, &depth, &imos](
auto dfs, const int par, const int ver) -> void {
bool has_multiple_edges = false;
for (const Edge<CostType>& e : graph[ver]) {
if (depth[e.dst] == -1) {
depth[e.dst] = depth[ver] + 1;
dfs(dfs, ver, e.dst);
if (imos[e.dst] == 0) {
res.emplace_back(std::min(ver, e.dst), std::max(ver, e.dst), e.cost);
}
imos[ver] += imos[e.dst];
} else if (!has_multiple_edges && e.dst == par) {
has_multiple_edges = true;
} else if (depth[e.dst] < depth[ver]) {
++imos[ver];
--imos[e.dst];
}
}
};
for (int i = 0; i < n; ++i) {
if (depth[i] == -1) {
depth[i] = 0;
dfs(dfs, -1, i);
}
}
return res;
}
} // namespace emthrm
#endif // EMTHRM_GRAPH_ENUMERATE_BRIDGES_HPP_
#line 1 "include/emthrm/graph/enumerate_bridges.hpp"
#include <algorithm>
#include <vector>
#line 1 "include/emthrm/graph/edge.hpp"
/**
* @title 辺
*/
#ifndef EMTHRM_GRAPH_EDGE_HPP_
#define EMTHRM_GRAPH_EDGE_HPP_
#include <compare>
namespace emthrm {
template <typename CostType>
struct Edge {
CostType cost;
int src, dst;
explicit Edge(const int src, const int dst, const CostType cost = 0)
: cost(cost), src(src), dst(dst) {}
auto operator<=>(const Edge& x) const = default;
};
} // namespace emthrm
#endif // EMTHRM_GRAPH_EDGE_HPP_
#line 8 "include/emthrm/graph/enumerate_bridges.hpp"
namespace emthrm {
template <typename CostType>
std::vector<Edge<CostType>> enumerate_bridges(
const std::vector<std::vector<Edge<CostType>>>& graph) {
const int n = graph.size();
std::vector<Edge<CostType>> res;
std::vector<int> depth(n, -1), imos(n, 0);
const auto dfs = [&graph, &res, &depth, &imos](
auto dfs, const int par, const int ver) -> void {
bool has_multiple_edges = false;
for (const Edge<CostType>& e : graph[ver]) {
if (depth[e.dst] == -1) {
depth[e.dst] = depth[ver] + 1;
dfs(dfs, ver, e.dst);
if (imos[e.dst] == 0) {
res.emplace_back(std::min(ver, e.dst), std::max(ver, e.dst), e.cost);
}
imos[ver] += imos[e.dst];
} else if (!has_multiple_edges && e.dst == par) {
has_multiple_edges = true;
} else if (depth[e.dst] < depth[ver]) {
++imos[ver];
--imos[e.dst];
}
}
};
for (int i = 0; i < n; ++i) {
if (depth[i] == -1) {
depth[i] = 0;
dfs(dfs, -1, i);
}
}
return res;
}
} // namespace emthrm