[골4] 1967 - 트리의 지름

#include <iostream>
#include <algorithm>
#include <vector>

using namespace std;

#define MAX 10002

vector<pair<int, int>> node[MAX];
bool vis[MAX];
int res, endPoint;

void DFS(int p = 1, int len = 0)
{
    if (vis[p])
        return;

    vis[p] = true;

    if (res < len)
    {
        res = len;
        endPoint = p;
    }
    for (int i = 0; i < node[p].size(); i++)
         DFS(node[p][i].first, len + node[p][i].second);
}

int main() 
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    int n; cin >> n;

    for (int i = 0; i < n - 1; i++)
    {
        int a, b, c; cin >> a >> b >> c;
        node[a].push_back({ b, c });
        node[b].push_back({ a, c });
    }
    DFS();
    res = 0;
    fill(vis, vis + MAX, false);
    DFS(endPoint);
    cout << res;
    return 0;
}