graph/dijkstra.hpp

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• Last update: 2022-08-26 11:10:48+09:00
• Include: #include "graph/dijkstra.hpp"

Depends on

• graph/graph.hpp

Code

#pragma once

#include "graph.hpp"

#include <queue>
#include <limits>
#include <functional>

template <typename T>
std::vector<T> dijkstra(const Graph<WeightedEdge<T>> &g, int s) {
    std::vector<T> dist(g.size(), std::numeric_limits<T>::max());
    std::priority_queue<std::pair<T, int>, std::vector<std::pair<T, int>>, std::greater<>> pq;
    dist[s] = T(0);
    pq.emplace(0, s);
    while (!pq.empty()) {
        auto [d, v] = pq.top();
        pq.pop();
        if (d > dist[v]) {
            continue;
        }
        for (const WeightedEdge<T> &e : g[v]) {
            if (d + e.wt < dist[e.to]) {
                dist[e.to] = d + e.wt;
                pq.emplace(dist[e.to], e.to);
            }
        }
    }
    return dist;
}

#line 2 "graph/dijkstra.hpp"

#line 2 "graph/graph.hpp"

#include <utility>
#include <vector>
#include <numeric>
#include <cassert>

template <typename Edge>
class Graph {
    std::vector<std::vector<Edge>> edges;

public:
    Graph() : edges() {}
    Graph(int v) : edges(v) {
        assert(v >= 0);
    }
    
    std::vector<int> add_vertices(int n) {
        int v = (int) edges.size();
        std::vector<int> idx(n);
        std::iota(idx.begin(), idx.end(), v);
        edges.resize(edges.size() + n);
        return idx;
    }

    template <typename... T>
    void add_directed_edge(int from, int to, T &&...val) {
        assert(from >= 0 && from < (int) edges.size());
        assert(to >= 0 && to < (int) edges.size());
        edges[from].emplace_back(Edge(to, std::forward<T>(val)...));
    }

    template <typename... T>
    void add_undirected_edge(int u, int v, const T &...val) {
        assert(u >= 0 && u < (int) edges.size());
        assert(v >= 0 && v < (int) edges.size());
        edges[u].emplace_back(Edge(v, val...));
        edges[v].emplace_back(Edge(u, val...));
    }

    int size() const {
        return (int) edges.size();
    }

    const std::vector<Edge> &operator[](int v) const {
        assert(v >= 0 && v < (int) edges.size());
        return edges[v];
    }

    std::vector<Edge> &operator[](int v) {
        assert(v >= 0 && v < (int) edges.size());
        return edges[v];
    }
};

struct UnweightedEdge {
    int to;

    UnweightedEdge(int t) : to(t) {}
    
    explicit operator int() const {
        return to;
    }

    using Weight = int;
    Weight weight() const {
        return 1;
    }
};

template <typename T>
struct WeightedEdge {
    int to;
    T wt;

    WeightedEdge(int t, const T &w) : to(t), wt(w) {}

    explicit operator int() const {
        return to;
    }

    using Weight = T;
    Weight weight() const {
        return wt;
    }
};

#line 4 "graph/dijkstra.hpp"

#include <queue>
#include <limits>
#include <functional>

template <typename T>
std::vector<T> dijkstra(const Graph<WeightedEdge<T>> &g, int s) {
    std::vector<T> dist(g.size(), std::numeric_limits<T>::max());
    std::priority_queue<std::pair<T, int>, std::vector<std::pair<T, int>>, std::greater<>> pq;
    dist[s] = T(0);
    pq.emplace(0, s);
    while (!pq.empty()) {
        auto [d, v] = pq.top();
        pq.pop();
        if (d > dist[v]) {
            continue;
        }
        for (const WeightedEdge<T> &e : g[v]) {
            if (d + e.wt < dist[e.to]) {
                dist[e.to] = d + e.wt;
                pq.emplace(dist[e.to], e.to);
            }
        }
    }
    return dist;
}

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