[BOJ] 1967 : 트리의 지름

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

const int n_ = 1e4 + 4;

struct edg { int idx, dst; };
int n, abc, sum;
vector<edg> gph[n_];

void dfs(int prv, int now, int dst) {
	if (sum < dst) sum = dst, abc = now;
	for (edg nxt : gph[now]) if (prv != nxt.idx)
		dfs(now, nxt.idx, dst + nxt.dst);
}

int main() {
	scanf("%d", &n);
	for (int i = 1, u, v, k; i < n; i++) {
		scanf("%d %d %d", &u, &v, &k);
		gph[u].push_back({ v,k });
		gph[v].push_back({ u,k });
	}

	abc = 1, dfs(0, abc, 0);
	sum = 0, dfs(0, abc, 0);

	printf("%d", sum);

	return 0;
}