Graph/tests/aizu_grl_5_a_tree_diameter.test.cpp

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Last update: 2022-11-21 21:56:30+08:00
Problem: https://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=GRL_5_A

Depends on

Code

#define PROBLEM "https://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=GRL_5_A"

#include "../../template.h"
#include "../tree_diameter.h"

void solve() {
    int n; cin >> n;
    vector<vector<pair<int,int>>> g(n);
    REP(i,n-1) {
        int u, v, cost; cin >> u >> v >> cost;
        g[u].emplace_back(v, cost);
        g[v].emplace_back(u, cost);
    }

    auto [length, path] = tree_diameter(g);
    cout << length << endl;
}

#line 1 "Graph/tests/aizu_grl_5_a_tree_diameter.test.cpp"
#define PROBLEM "https://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=GRL_5_A"

#line 1 "template.h"
#include <bits/stdc++.h>
using namespace std;

#define FOR(i,a,b) for(int i=(a),_b=(b); i<=_b; i++)
#define FORD(i,a,b) for(int i=(a),_b=(b); i>=_b; i--)
#define REP(i,a) for(int i=0,_a=(a); i<_a; i++)
#define EACH(it,a) for(__typeof(a.begin()) it = a.begin(); it != a.end(); ++it)

#define DEBUG(x) { cout << #x << " = "; cout << (x) << endl; }
#define PR(a,n) { cout << #a << " = "; FOR(_,1,n) cout << a[_] << ' '; cout << endl; }
#define PR0(a,n) { cout << #a << " = "; REP(_,n) cout << a[_] << ' '; cout << endl; }

#define sqr(x) ((x) * (x))

// For printing pair, container, etc.
// Copied from https://quangloc99.github.io/2021/07/30/my-CP-debugging-template.html
template<class U, class V> ostream& operator << (ostream& out, const pair<U, V>& p) {
    return out << '(' << p.first << ", " << p.second << ')';
}

template<class Con, class = decltype(begin(declval<Con>()))>
typename enable_if<!is_same<Con, string>::value, ostream&>::type
operator << (ostream& out, const Con& con) {
    out << '{';
    for (auto beg = con.begin(), it = beg; it != con.end(); it++) {
        out << (it == beg ? "" : ", ") << *it;
    }
    return out << '}';
}
template<size_t i, class T> ostream& print_tuple_utils(ostream& out, const T& tup) {
    if constexpr(i == tuple_size<T>::value) return out << ")"; 
    else return print_tuple_utils<i + 1, T>(out << (i ? ", " : "(") << get<i>(tup), tup); 
}
template<class ...U> ostream& operator << (ostream& out, const tuple<U...>& t) {
    return print_tuple_utils<0, tuple<U...>>(out, t);
}

mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
long long get_rand(long long r) {
    return uniform_int_distribution<long long> (0, r-1)(rng);
}

template<typename T>
vector<T> read_vector(int n) {
    vector<T> res(n);
    for (int& x : res) cin >> x;
    return res;
}

void solve();

int main() {
    ios::sync_with_stdio(0); cin.tie(0);
    solve();
    return 0;
}
#line 1 "Graph/tree_diameter.h"
// Index from 0
// g should contains both (u, v) and (v, u)
// Return {length, path}
//
// Tested:
// - https://judge.yosupo.jp/problem/tree_diameter
//
// Tree diameter (weighted) {{{
using ll = long long;
pair<ll, vector<int>> tree_diameter(const vector<vector<pair<int,int>>>& g) {
    int n = g.size();
    vector<ll> dist(n);
    vector<int> parent(n);

    function<void(int, int, ll)> dfs = [&] (int u, int fu, ll cur_dist) {
        dist[u] = cur_dist;
        parent[u] = fu;
        for (auto [v, cost] : g[u]) if (v != fu) {
            dfs(v, u, cur_dist + cost);
        }
    };
    dfs(0, -1, 0);
    // r = furthest node from root
    int r = max_element(dist.begin(), dist.end()) - dist.begin();
    dfs(r, -1, 0);
    // r->s = longest path
    int s = max_element(dist.begin(), dist.end()) - dist.begin();

    vector<int> path;
    for (int x = s; x >= 0; x = parent[x]) path.push_back(x);

    return {dist[s], path};
}
// }}}
#line 5 "Graph/tests/aizu_grl_5_a_tree_diameter.test.cpp"

void solve() {
    int n; cin >> n;
    vector<vector<pair<int,int>>> g(n);
    REP(i,n-1) {
        int u, v, cost; cin >> u >> v >> cost;
        g[u].emplace_back(v, cost);
        g[v].emplace_back(u, cost);
    }

    auto [length, path] = tree_diameter(g);
    cout << length << endl;
}