🐣 문제

링크 : https://www.acmicpc.net/problem/1167

🐥 코드

/*
문제 : 트리의 지름 
링크 : https://www.acmicpc.net/problem/1167
*/

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

vector<pair<int, int>> v[100001];
bool visited[100001];

int maxDis, maxNode;
void dfs(int node, int dis){
    if(visited[node]) return;

    if(maxDis < dis){
        maxDis = dis;
        maxNode = node;
    }

    visited[node] = true;

    for(int i = 0; i < v[node].size(); i++){
        int a = v[node][i].first;
        int b = v[node][i].second;
        dfs(a, b + dis);
    }
}

int main(){
    int n;
    cin >> n;
    int from, to, dis;
    for(int i = 0; i < n; i++){
        cin >> from;
        while(true){
            cin >> to;
            if(to == -1) break;
            cin >> dis;
            v[from].push_back({to, dis});
            v[to].push_back({from,dis});
        }
    }

    dfs(1,0);

    for(int i = 0; i <= n; i++){
        visited[i] = false;
    }

    dfs(maxNode, 0);

    cout << maxDis;
    return 0;
}