1094_Farthest_Nodes_in_a_Tree.md

Algorithm: Diameter_of_Tree_or_BFS_and_DFS

Problem: 1094 Farthest Nodes in a Tree

#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define vi vector<int>
#define pii pair<int, int>
#define pll pair<ll, ll>
#define vvi vector<vi>
#define vll vector<ll>
#define vvll vector<vector<ll>>
#define vpii vector<pair<int,int>>
#define vpll vector<pair<ll,ll>>
#define vb vector<bool>
#define vs vector<string>
///............x...........///
#define all(a) a.begin(), a.end()
#define allr(a) a.rbegin(), a.rend()
#define mp(a, b) make_pair(a, b)
#define pb push_back
#define ff first
#define ss second
#define bg begin()
#define UNIQUE(X) (X).erase(unique(all(X)), (X).end())
#define ft cout << "for test"<<endl;
#define read(v, a, n) for (int i = a; i<n; i++)cin>>v[i];
#define print(v) for (auto it : v)cout << it<<endl//' ';cout << endl;
#define PI acos(-1.0)
#define yes cout <<"Yes"<< endl
#define no cout<<"No"<<endl
#define FIO ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define t_c int test, cs = 1;cin>>test;while (test--)
#define casep cout<<"Case "<< cs++<<": ";
///................function.....................///

#define D(a) (double)(a)
#define sqr(a) (a * a)
#define siz(s) (int)(s.size())
#define max3(a, b, c) max(a, max(b, c))
#define min3(a, b, c) min(a, min(b, c))
#define Min(a) *min_element(all(a))
#define mod 100000007
///.........Graph.........///
int X[] = {1, -1, 0, 0};
int Y[] = {0, 0, 1, -1};
///........constant........///
const ll N = 4e8+5;
int main(){
	FIO;
	t_c{
		int n,i,j;
		cin>>n;
		vector<vpii> g(n);
		int a,b,c;
		for(i=1; i<n; i++){
			cin>>a>>b>>c;
			g[a].pb({b,c});
			g[b].pb({a,c});
		}
		queue<int>q;
		q.push(0);
		vi dis(n,-1);
		dis[0]=0;
		int node,mx=0;
		while(!q.empty()){
			int u=q.front();
			q.pop();
			for(auto to:g[u]){
				if(dis[to.ff]==-1){
					dis[to.ff]=dis[u]+to.ss;
					q.push(to.ff);
					if(mx<dis[to.ff]){
						mx = dis[to.ff];
						node=to.ff;
					}
				}
			}
		}
		q.push(node);
		fill(all(dis),-1);
		dis[node]=0;
		while(!q.empty()){
			int u=q.front();
			q.pop();
			for(auto to:g[u]){
				if(dis[to.ff]==-1){
					dis[to.ff]=dis[u]+to.ss;
					q.push(to.ff);
					mx = max(mx,dis[to.ff]);
				}
			}
		}
		casep;
		cout<<mx<<endl;
	}
}