Library

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:heavy_check_mark: test/tree/Tree_Diameter.test.cpp

Depends on

Code

#define PROBLEM "https://judge.yosupo.jp/problem/tree_diameter"

#include "../../tree/tree_diameter.hpp"

#include <iostream>

#include "../../graph/base.hpp"
#include "../../template/int_alias.hpp"

using ebi::i64;

int main() {
    int n;
    std::cin >> n;
    ebi::Graph<i64> g(n);
    g.read_tree(0, true);
    auto [x, path] = ebi::tree_diameter(g);
    std::cout << x << " " << path.size() << '\n';
    for (auto v : path) {
        std::cout << v << " ";
    }
    std::cout << '\n';
}
#line 1 "test/tree/Tree_Diameter.test.cpp"
#define PROBLEM "https://judge.yosupo.jp/problem/tree_diameter"

#line 2 "tree/tree_diameter.hpp"

#include <algorithm>
#include <vector>

#line 2 "graph/base.hpp"

#include <cassert>
#include <iostream>
#include <ranges>
#line 7 "graph/base.hpp"

#line 2 "data_structure/simple_csr.hpp"

#line 4 "data_structure/simple_csr.hpp"
#include <utility>
#line 6 "data_structure/simple_csr.hpp"

namespace ebi {

template <class E> struct simple_csr {
    simple_csr() = default;

    simple_csr(int n, const std::vector<std::pair<int, E>>& elements)
        : start(n + 1, 0), elist(elements.size()) {
        for (auto e : elements) {
            start[e.first + 1]++;
        }
        for (auto i : std::views::iota(0, n)) {
            start[i + 1] += start[i];
        }
        auto counter = start;
        for (auto [i, e] : elements) {
            elist[counter[i]++] = e;
        }
    }

    simple_csr(const std::vector<std::vector<E>>& es)
        : start(es.size() + 1, 0) {
        int n = es.size();
        for (auto i : std::views::iota(0, n)) {
            start[i + 1] = (int)es[i].size() + start[i];
        }
        elist.resize(start.back());
        for (auto i : std::views::iota(0, n)) {
            std::copy(es[i].begin(), es[i].end(), elist.begin() + start[i]);
        }
    }

    int size() const {
        return (int)start.size() - 1;
    }

    const auto operator[](int i) const {
        return std::ranges::subrange(elist.begin() + start[i],
                                     elist.begin() + start[i + 1]);
    }
    auto operator[](int i) {
        return std::ranges::subrange(elist.begin() + start[i],
                                     elist.begin() + start[i + 1]);
    }

    const auto operator()(int i, int l, int r) const {
        return std::ranges::subrange(elist.begin() + start[i] + l,
                                     elist.begin() + start[i + 1] + r);
    }
    auto operator()(int i, int l, int r) {
        return std::ranges::subrange(elist.begin() + start[i] + l,
                                     elist.begin() + start[i + 1] + r);
    }

  private:
    std::vector<int> start;
    std::vector<E> elist;
};

}  // namespace ebi
#line 9 "graph/base.hpp"

namespace ebi {

template <class T> struct Edge {
    int from, to;
    T cost;
    int id;
};

template <class E> struct Graph {
    using cost_type = E;
    using edge_type = Edge<cost_type>;

    Graph(int n_) : n(n_) {}

    Graph() = default;

    void add_edge(int u, int v, cost_type c) {
        buff.emplace_back(u, edge_type{u, v, c, m});
        edges.emplace_back(edge_type{u, v, c, m++});
    }

    void add_undirected_edge(int u, int v, cost_type c) {
        buff.emplace_back(u, edge_type{u, v, c, m});
        buff.emplace_back(v, edge_type{v, u, c, m});
        edges.emplace_back(edge_type{u, v, c, m});
        m++;
    }

    void read_tree(int offset = 1, bool is_weighted = false) {
        read_graph(n - 1, offset, false, is_weighted);
    }

    void read_parents(int offset = 1) {
        for (auto i : std::views::iota(1, n)) {
            int p;
            std::cin >> p;
            p -= offset;
            add_undirected_edge(p, i, 1);
        }
        build();
    }

    void read_graph(int e, int offset = 1, bool is_directed = false,
                    bool is_weighted = false) {
        for (int i = 0; i < e; i++) {
            int u, v;
            std::cin >> u >> v;
            u -= offset;
            v -= offset;
            if (is_weighted) {
                cost_type c;
                std::cin >> c;
                if (is_directed) {
                    add_edge(u, v, c);
                } else {
                    add_undirected_edge(u, v, c);
                }
            } else {
                if (is_directed) {
                    add_edge(u, v, 1);
                } else {
                    add_undirected_edge(u, v, 1);
                }
            }
        }
        build();
    }

    void build() {
        assert(!prepared);
        csr = simple_csr<edge_type>(n, buff);
        buff.clear();
        prepared = true;
    }

    int size() const {
        return n;
    }

    int node_number() const {
        return n;
    }

    int edge_number() const {
        return m;
    }

    edge_type get_edge(int i) const {
        return edges[i];
    }

    std::vector<edge_type> get_edges() const {
        return edges;
    }

    const auto operator[](int i) const {
        return csr[i];
    }
    auto operator[](int i) {
        return csr[i];
    }

  private:
    int n, m = 0;

    std::vector<std::pair<int,edge_type>> buff;

    std::vector<edge_type> edges;
    simple_csr<edge_type> csr;
    bool prepared = false;
};

}  // namespace ebi
#line 7 "tree/tree_diameter.hpp"

namespace ebi {

template <class T>
std::pair<T, std::vector<int>> tree_diameter(const Graph<T> &g) {
    int n = g.size();
    std::vector<T> dp(n);
    std::vector<int> par(n, -1);
    dp[0] = 0;
    auto dfs = [&](auto &&self, int v) -> void {
        for (const auto e: g[v]) {
            if (e.to == par[v]) continue;
            par[e.to] = v;
            dp[e.to] = dp[v] + e.cost;
            self(self, e.to);
        }
    };
    dfs(dfs, 0);
    int u = std::max_element(dp.begin(), dp.end()) - dp.begin();
    par[u] = -1;
    dp[u] = 0;
    dfs(dfs, u);
    int v = std::max_element(dp.begin(), dp.end()) - dp.begin();
    std::vector<int> path;
    while (u != v) {
        path.emplace_back(v);
        v = par[v];
    }
    path.emplace_back(u);
    return {dp[*path.begin()], path};
}

}  // namespace ebi
#line 4 "test/tree/Tree_Diameter.test.cpp"

#line 6 "test/tree/Tree_Diameter.test.cpp"

#line 2 "template/int_alias.hpp"

#include <cstdint>

namespace ebi {

using ld = long double;
using std::size_t;
using i8 = std::int8_t;
using u8 = std::uint8_t;
using i16 = std::int16_t;
using u16 = std::uint16_t;
using i32 = std::int32_t;
using u32 = std::uint32_t;
using i64 = std::int64_t;
using u64 = std::uint64_t;
using i128 = __int128_t;
using u128 = __uint128_t;

}  // namespace ebi
#line 9 "test/tree/Tree_Diameter.test.cpp"

using ebi::i64;

int main() {
    int n;
    std::cin >> n;
    ebi::Graph<i64> g(n);
    g.read_tree(0, true);
    auto [x, path] = ebi::tree_diameter(g);
    std::cout << x << " " << path.size() << '\n';
    for (auto v : path) {
        std::cout << v << " ";
    }
    std::cout << '\n';
}
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