Problem p03654 (C++)

Buggy submission (status: Time Limit Exceeded):
// #define _GLIBCXX_DEBUG

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

#define endl '\n'
#define lfs cout << fixed << setprecision(10)
#define ALL(a) (a).begin(), (a).end()
#define ALLR(a) (a).rbegin(), (a).rend()
#define spa << " " <<
#define fi first
#define se second
#define MP make_pair
#define MT make_tuple
#define PB push_back
#define EB emplace_back
#define rep(i, n, m) for (ll i = (n); i < (ll)(m); i++)
#define rrep(i, n, m) for (ll i = (ll)(m)-1; i >= (ll)(n); i--)
using ll = long long;
using ld = long double;
const ll MOD1 = 1e9 + 7;
const ll MOD9 = 998244353;
const ll INF = 1e18;
using P = pair<ll, ll>;
template <typename T1, typename T2> bool chmin(T1 &a, T2 b) {
  if (a > b) {
    a = b;
    return true;
  } else
    return false;
}
template <typename T1, typename T2> bool chmax(T1 &a, T2 b) {
  if (a < b) {
    a = b;
    return true;
  } else
    return false;
}
ll median(ll a, ll b, ll c) {
  return a + b + c - max({a, b, c}) - min({a, b, c});
}
void ans1(bool x) {
  if (x)
    cout << "Yes" << endl;
  else
    cout << "No" << endl;
}
void ans2(bool x) {
  if (x)
    cout << "YES" << endl;
  else
    cout << "NO" << endl;
}
void ans3(bool x) {
  if (x)
    cout << "Yay!" << endl;
  else
    cout << ":(" << endl;
}
template <typename T1, typename T2> void ans(bool x, T1 y, T2 z) {
  if (x)
    cout << y << endl;
  else
    cout << z << endl;
}
template <typename T> void debug(vector<vector<T>> &v, ll h, ll w) {
  for (ll i = 0; i < h; i++) {
    cout << v[i][0];
    for (ll j = 1; j < w; j++)
      cout spa v[i][j];
    cout << endl;
  }
};
void debug(vector<string> &v, ll h, ll w) {
  for (ll i = 0; i < h; i++) {
    for (ll j = 0; j < w; j++)
      cout << v[i][j];
    cout << endl;
  }
};
template <typename T> void debug(vector<T> &v, ll n) {
  if (n != 0)
    cout << v[0];
  for (ll i = 1; i < n; i++)
    cout spa v[i];
  cout << endl;
};
template <typename T> vector<vector<T>> vec(ll x, ll y, T w) {
  vector<vector<T>> v(x, vector<T>(y, w));
  return v;
}
ll gcd(ll x, ll y) {
  ll r;
  while (y != 0 && (r = x % y) != 0) {
    x = y;
    y = r;
  }
  return y == 0 ? x : y;
}
vector<ll> dx = {1, 0, -1, 0, 1, 1, -1, -1};
vector<ll> dy = {0, 1, 0, -1, 1, -1, 1, -1};
template <typename T> vector<T> make_v(size_t a, T b) {
  return vector<T>(a, b);
}
template <typename... Ts> auto make_v(size_t a, Ts... ts) {
  return vector<decltype(make_v(ts...))>(a, make_v(ts...));
}
template <typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) {
  return os << p.first << " " << p.second;
}
struct edge {
  ll to = -1, cost = 0;
  edge(){};
  edge(ll t, ll c) : to(t), cost(c){};
};
struct CentroidDecomposition {
  ll n;
  const vector<vector<edge>> &g;
  vector<bool> used; // 既に重心として選ばれたか
  vector<ll> sub;    // 部分木のサイズ
  CentroidDecomposition(const vector<vector<edge>> &g) : g(g) {
    n = g.size();
    sub.assign(g.size(), 0);
    used.assign(g.size(), false);
  }
  ll search_centroid(ll root) {
    return dfs_search(root, -1, dfs_sz(root, -1) / 2);
  }
  ll dfs_sz(ll k, ll par) {
    sub[k] = 1;
    for (auto e : g[k]) {
      if (e.to == par || used[e.to])
        continue;
      sub[k] += dfs_sz(e.to, k);
    }
    return sub[k];
  }
  ll dfs_search(ll k, ll par, ll mid) {
    for (auto e : g[k]) {
      if (e.to == par || used[e.to])
        continue;
      if (sub[e.to] > mid)
        return dfs_search(e.to, k, mid);
    }
    return k;
  }
  vector<ll> centroid_enum(ll root) {
    vector<ll> ret;
    ret.push_back(search_centroid(root));
    auto sub2 = sub;
    for (auto e : g[ret[0]]) {
      if (used[e.to] || sub2[e.to] == sub2[ret[0]])
        continue;
      ll c = search_centroid(e.to);
      if (c != ret[0])
        ret.push_back(c);
    }
    return ret;
  }
  void run() {
    // 何か前処理を書くなら

    solve(0);
  }

  void solve(ll root) {
    ll cent = search_centroid(root);
    ll size = sub[root];
    used[cent] = true;
    vector<vector<ll>> ver;
    for (auto e : g[cent]) {
      if (!used[e.to]) {
        ver.emplace_back();
        dfs(e.to, -1, ver.back());
      }
    }

    for (auto e : g[cent]) {
      if (!used[e.to]) {
        solve(e.to);
      }
    }
    used[cent] = false;

    return; // 統治するなら何か返す
  }
  void dfs(ll k, ll par, vector<ll> &ver) {
    ver.push_back(k);
    for (auto e : g[k]) {
      if (e.to == par || used[e.to])
        continue;
      dfs(e.to, k, ver);
    }
  }
};
ll ret = 0;
void dfs(ll k, vector<vector<edge>> &g, ll par, ll d) {
  ret += 2 * d;
  for (auto e : g[k]) {
    if (par != e.to) {
      dfs(e.to, g, k, d + e.cost);
    }
  }
}
int main() {
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);
  ll res = 0, buf = 0;
  bool judge = true;
  ll n;
  cin >> n;
  vector<vector<edge>> g(n);
  rep(i, 0, n - 1) {
    ll a, b, c;
    cin >> a >> b >> c;
    a--;
    b--;
    g[a].EB(b, c);
    g[b].EB(a, c);
  }
  CentroidDecomposition cent(g);
  auto r = cent.centroid_enum(0);
  dfs(r[0], g, -1, 0);
  if (r.size() == 2) {
    for (auto e : g[r[0]]) {
      if (e.to == r[1])
        ret -= e.cost;
    }
  } else {
    ll mi = INF;
    for (auto e : g[r[0]]) {
      chmin(mi, e.cost);
    }
    ret -= mi;
  }
  // debug(r,r.size());
  cout << ret << endl;
  return 0;
}

Fixed submission:
// #define _GLIBCXX_DEBUG

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

#define endl '\n'
#define lfs cout << fixed << setprecision(10)
#define ALL(a) (a).begin(), (a).end()
#define ALLR(a) (a).rbegin(), (a).rend()
#define spa << " " <<
#define fi first
#define se second
#define MP make_pair
#define MT make_tuple
#define PB push_back
#define EB emplace_back
#define rep(i, n, m) for (ll i = (n); i < (ll)(m); i++)
#define rrep(i, n, m) for (ll i = (ll)(m)-1; i >= (ll)(n); i--)
using ll = long long;
using ld = long double;
const ll MOD1 = 1e9 + 7;
const ll MOD9 = 998244353;
const ll INF = 1e18;
using P = pair<ll, ll>;
template <typename T1, typename T2> bool chmin(T1 &a, T2 b) {
  if (a > b) {
    a = b;
    return true;
  } else
    return false;
}
template <typename T1, typename T2> bool chmax(T1 &a, T2 b) {
  if (a < b) {
    a = b;
    return true;
  } else
    return false;
}
ll median(ll a, ll b, ll c) {
  return a + b + c - max({a, b, c}) - min({a, b, c});
}
void ans1(bool x) {
  if (x)
    cout << "Yes" << endl;
  else
    cout << "No" << endl;
}
void ans2(bool x) {
  if (x)
    cout << "YES" << endl;
  else
    cout << "NO" << endl;
}
void ans3(bool x) {
  if (x)
    cout << "Yay!" << endl;
  else
    cout << ":(" << endl;
}
template <typename T1, typename T2> void ans(bool x, T1 y, T2 z) {
  if (x)
    cout << y << endl;
  else
    cout << z << endl;
}
template <typename T> void debug(vector<vector<T>> &v, ll h, ll w) {
  for (ll i = 0; i < h; i++) {
    cout << v[i][0];
    for (ll j = 1; j < w; j++)
      cout spa v[i][j];
    cout << endl;
  }
};
void debug(vector<string> &v, ll h, ll w) {
  for (ll i = 0; i < h; i++) {
    for (ll j = 0; j < w; j++)
      cout << v[i][j];
    cout << endl;
  }
};
template <typename T> void debug(vector<T> &v, ll n) {
  if (n != 0)
    cout << v[0];
  for (ll i = 1; i < n; i++)
    cout spa v[i];
  cout << endl;
};
template <typename T> vector<vector<T>> vec(ll x, ll y, T w) {
  vector<vector<T>> v(x, vector<T>(y, w));
  return v;
}
ll gcd(ll x, ll y) {
  ll r;
  while (y != 0 && (r = x % y) != 0) {
    x = y;
    y = r;
  }
  return y == 0 ? x : y;
}
vector<ll> dx = {1, 0, -1, 0, 1, 1, -1, -1};
vector<ll> dy = {0, 1, 0, -1, 1, -1, 1, -1};
template <typename T> vector<T> make_v(size_t a, T b) {
  return vector<T>(a, b);
}
template <typename... Ts> auto make_v(size_t a, Ts... ts) {
  return vector<decltype(make_v(ts...))>(a, make_v(ts...));
}
template <typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) {
  return os << p.first << " " << p.second;
}
struct edge {
  ll to = -1, cost = 0;
  edge(){};
  edge(ll t, ll c) : to(t), cost(c){};
};
struct CentroidDecomposition {
  ll n;
  const vector<vector<edge>> &g;
  vector<bool> used; // 既に重心として選ばれたか
  vector<ll> sub;    // 部分木のサイズ
  CentroidDecomposition(const vector<vector<edge>> &g) : g(g) {
    n = g.size();
    sub.assign(g.size(), 0);
    used.assign(g.size(), false);
  }
  ll search_centroid(ll root) {
    return dfs_search(root, -1, dfs_sz(root, -1) / 2);
  }
  ll dfs_sz(ll k, ll par) {
    sub[k] = 1;
    for (auto e : g[k]) {
      if (e.to == par || used[e.to])
        continue;
      sub[k] += dfs_sz(e.to, k);
    }
    return sub[k];
  }
  ll dfs_search(ll k, ll par, ll mid) {
    for (auto e : g[k]) {
      if (e.to == par || used[e.to])
        continue;
      if (sub[e.to] > mid)
        return dfs_search(e.to, k, mid);
    }
    return k;
  }
  vector<ll> centroid_enum(ll root) {
    vector<ll> ret;
    ret.push_back(search_centroid(root));
    auto sub2 = sub;
    for (auto e : g[ret[0]]) {
      if (used[e.to] || n != 2 * sub2[e.to])
        continue;
      ll c = search_centroid(e.to);
      if (c != ret[0])
        ret.push_back(c);
    }
    return ret;
  }
  void run() {
    // 何か前処理を書くなら

    solve(0);
  }

  void solve(ll root) {
    ll cent = search_centroid(root);
    ll size = sub[root];
    used[cent] = true;
    vector<vector<ll>> ver;
    for (auto e : g[cent]) {
      if (!used[e.to]) {
        ver.emplace_back();
        dfs(e.to, -1, ver.back());
      }
    }

    for (auto e : g[cent]) {
      if (!used[e.to]) {
        solve(e.to);
      }
    }
    used[cent] = false;

    return; // 統治するなら何か返す
  }
  void dfs(ll k, ll par, vector<ll> &ver) {
    ver.push_back(k);
    for (auto e : g[k]) {
      if (e.to == par || used[e.to])
        continue;
      dfs(e.to, k, ver);
    }
  }
};
ll ret = 0;
void dfs(ll k, vector<vector<edge>> &g, ll par, ll d) {
  ret += 2 * d;
  for (auto e : g[k]) {
    if (par != e.to) {
      dfs(e.to, g, k, d + e.cost);
    }
  }
}
int main() {
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);
  ll res = 0, buf = 0;
  bool judge = true;
  ll n;
  cin >> n;
  vector<vector<edge>> g(n);
  rep(i, 0, n - 1) {
    ll a, b, c;
    cin >> a >> b >> c;
    a--;
    b--;
    g[a].EB(b, c);
    g[b].EB(a, c);
  }
  CentroidDecomposition cent(g);
  auto r = cent.centroid_enum(0);
  dfs(r[0], g, -1, 0);
  if (r.size() == 2) {
    for (auto e : g[r[0]]) {
      if (e.to == r[1])
        ret -= e.cost;
    }
  } else {
    ll mi = INF;
    for (auto e : g[r[0]]) {
      chmin(mi, e.cost);
    }
    ret -= mi;
  }
  // debug(r,r.size());
  cout << ret << endl;
  return 0;
}