2*所有边的权值 - 最长的路径权值

#include<bits/stdc++.h>
using namespace std;
using ll = long long;

const ll N = 1e5 + 5;
ll n;
vector<pair<ll, ll>> g[N];
ll dist[N];//记录每个点距离起点的距离

void dfs(ll u, ll fa) {//当前的点 当前点的父节点
    for (auto [v, w] : g[u]) {
        if (v == fa) continue;//不走回头路
        dist[v] = dist[u] + w;
        dfs(v, u);
    }
}

int main() {
    cin >> n;
    ll sum = 0;
    for (ll i = 1; i < n; i++) {
        ll u, v, w;
        cin >> u >> v >> w;
        g[u].push_back({v, w});
        g[v].push_back({u, w});
        sum += w;
    }
    
    dfs(1, 0);
    
    ll max_dist = 0;
    for (ll i = 1; i <= n; i++) {
        max_dist = max(max_dist, dist[i]);
    }
    
    cout << 2 * sum - max_dist << endl;
    return 0;
}