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OI-codes/AcWing/1072/1072.cpp

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#include <iostream>
#include <vector>
using std::cin;
using std::cout;
const char endl = '\n';
const int N = 10005;
int n, ans;
std::vector<std::pair<int, int>> g[N];
int dfs(int u, int fa) {
int d1 = 0, d2 = 0;
for (auto e : g[u]) {
int v = e.first,
w = e.second;
if (v == fa) continue;
int d = dfs(v, u) + w;
if (d >= d1) {
d2 = d1;
d1 = d;
} else if (d > d2) {
d2 = d;
}
}
ans = std::max(ans, d1 + d2);
return d1;
}
int main() {
std::ios::sync_with_stdio(false);
cin >> n;
for (int i = 1, u, v, w; i < n; i++) {
cin >> u >> v >> w;
g[u].push_back(std::make_pair(v, w));
g[v].push_back(std::make_pair(u, w));
}
dfs(1, -1);
cout << ans << endl;
return 0;
}