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#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; }