/** * author: otera * created: 05.02.2022 03:04:09 **/ #include #include #include namespace otera { class LCA { public: LCA(const std::vector> &g, int root = 0) { int _n = (int)g.size(); int _N = 1; while((1<<_N) < _n) ++ _N; parent.assign(_N, std::vector(_n, -1)); dep.assign(_n, -1); dfs(g, root); for(int i = 0; i + 1 < (int)parent.size(); ++ i) { for(int v = 0; v < _n; ++ v) { if(parent[i][v] != -1) { parent[i + 1][v] = parent[i][parent[i][v]]; } } } } int lca(int u, int v) const { if(dep[u] > dep[v]) std::swap(u, v); for(int i = 0; i < (int)parent.size(); ++ i) { if((dep[u] - dep[v]) & (1<= 0; -- i) { if(parent[i][u] != parent[i][v]) { u = parent[i][u]; v = parent[i][v]; } } return parent[0][u]; } int depth(int u) const { return dep[u]; } int dist(int u, int v) const { return dep[u] + dep[v] - 2 * dep[operator()(u, v)]; } int operator()(int u, int v) const { return lca(u, v); } private: std::vector dep; std::vector> parent; void dfs(const std::vector> &g, int root) { auto rec = [&](auto &&self, int v, int p, int d) -> void { dep[v] = d; parent[0][v] = p; for(int nv: g[v]) { if(nv == p) continue; self(self, nv, v, d + 1); } }; rec(rec, root, -1, 0); } }; } // namespace otera namespace otera { template struct Compressor { public: static constexpr int absent = -1; Compressor() : _xs(std::vector{}) {} Compressor(const std::vector &vs) { add(vs); build(); } void add(const std::vector &vs) { std::copy(vs.begin(), vs.end(), std::back_inserter(_xs)); } void add(const T &e) { _xs.emplace_back(e); } void build() { std::sort(_xs.begin(), _xs.end()); _xs.erase(std::unique(_xs.begin(), _xs.end()), _xs.end()); } int size() const { return _xs.size(); } bool has_key(const T &e) const { return std::binary_search(_xs.begin(), _xs.end(), e); } std::vector get(const std::vector &vs) const { std::vector res; std::transform(vs.begin(), vs.end(), std::back_inserter(res), [&](const T &e) { return get(e); }); return res; } int get(const T &e, int default_value = absent) const { const int id = min_geq_index(e); return id != size() and _xs[id] == e ? id : default_value; } const T &operator[](int compressed_index) const { return _xs[compressed_index]; } T min_gt(const T &e, const T &default_value) const { auto it = std::upper_bound(_xs.begin(), _xs.end(), e); return it == _xs.end() ? default_value : *it; } T min_geq(const T &e, const T &default_value) const { auto it = std::lower_bound(_xs.begin(), _xs.end(), e); return it == _xs.end() ? default_value : *it; } T max_lt(const T &e, const T &default_value) const { auto it = std::lower_bound(_xs.begin(), _xs.end(), e); return it == _xs.begin() ? default_value : *std::prev(it); } T max_leq(const T &e, const T &default_value) const { auto it = std::upper_bound(_xs.begin(), _xs.end(), e); return it == _xs.begin() ? default_value : *std::prev(it); } int min_gt_index(const T &e) const { return std::upper_bound(_xs.begin(), _xs.end(), e) - _xs.begin(); } int min_geq_index(const T &e) const { return std::lower_bound(_xs.begin(), _xs.end(), e) - _xs.begin(); } int max_lt_index(const T &e) const { return int(std::lower_bound(_xs.begin(), _xs.end(), e)- _xs.begin()) - 1; } int max_leq_index(const T &e) const { return int(std::lower_bound(_xs.begin(), _xs.end(), e)- _xs.begin()) - 1; } private: std::vector _xs; }; } // namespace otera using namespace std; using ll = long long; using ld = long double; using ull = unsigned long long; using uint = unsigned; #define repa(i, n) for(int i = 0; i < n; ++ i) #define repb(i, a, b) for(int i = a; i < b; ++ i) #define repc(i, a, b, c) for(int i = a; i < b; i += c) #define overload4(a, b, c, d, e, ...) e #define rep(...) overload4(__VA_ARGS__, repc, repb, repa)(__VA_ARGS__) #define rep1a(i, n) for(int i = 0; i <= n; ++ i) #define rep1b(i, a, b) for(int i = a; i <= b; ++ i) #define rep1c(i, a, b, c) for(int i = a; i <= b; i += c) #define rep1(...) overload4(__VA_ARGS__, rep1c, rep1b, rep1a)(__VA_ARGS__) #define per(i,n) for(int i=n-1;i>=0;i--) #define per1(i,n) for(int i=n;i>=1;i--) typedef pair P; typedef pair LP; #define pb push_back #define eb emplace_back #define fr first #define sc second #define all(c) c.begin(),c.end() #define lb(c, x) distance((c).begin(), lower_bound(all(c), (x))) #define ub(c, x) distance((c).begin(), upper_bound(all(c), (x))) #define Sort(a) sort(all(a)) #define Rev(a) reverse(all(a)) #define Uniq(a) sort(all(a));a.erase(unique(all(a)),end(a)) #define si(c) (int)(c).size() inline ll popcnt(ull a){ return __builtin_popcountll(a); } #define tpow(n) (1LL<<(n)) #define unless(A) if(!(A)) ll intpow(ll a, ll b){ ll ans = 1; while(b){ if(b & 1) ans *= a; a *= a; b /= 2; } return ans; } ll intpow(ll a, ll b, ll m) {ll ans = 1; while(b){ if(b & 1) (ans *= a) %= m; (a *= a) %= m; b /= 2; } return ans; } template inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; } template inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; } #define INT(...) int __VA_ARGS__;in(__VA_ARGS__) #define LL(...) ll __VA_ARGS__;in(__VA_ARGS__) #define ULL(...) ull __VA_ARGS__;in(__VA_ARGS__) #define STR(...) string __VA_ARGS__;in(__VA_ARGS__) #define CHR(...) char __VA_ARGS__;in(__VA_ARGS__) #define DBL(...) double __VA_ARGS__;in(__VA_ARGS__) #define LD(...) ld __VA_ARGS__;in(__VA_ARGS__) #define vec(type,name,...) vectorname(__VA_ARGS__) #define VEC(type,name,size) vectorname(size);in(name) #define vv(type,name,h,...) vector>name(h,vector(__VA_ARGS__)) #define VV(type,name,h,w) vector>name(h,vector(w));in(name) #define vvv(type,name,h,w,...) vector>>name(h,vector>(w,vector(__VA_ARGS__))) template using vc = vector; template using vvc = vector>; template using vvvc = vector>; template using vvvvc = vector>; template using pq = priority_queue; template using pqg = priority_queue, greater>; template void scan(T& a){ cin >> a; } template void scan(vector& a){ for(auto&& i : a) scan(i); } void in(){} template void in(Head& head, Tail&... tail){ scan(head); in(tail...); } void print(){ cout << ' '; } template void print(const T& a){ cout << a; } template void print(const vector& a){ if(a.empty()) return; print(a[0]); for(auto i = a.begin(); ++i != a.end(); ){ cout << ' '; print(*i); } } int out(){ cout << '\n'; return 0; } template int out(const T& t){ print(t); cout << '\n'; return 0; } template int out(const Head& head, const Tail&... tail){ print(head); cout << ' '; out(tail...); return 0; } #define CHOOSE(a) CHOOSE2 a #define CHOOSE2(a0,a1,a2,a3,a4,x,...) x #define debug_1(x1) cout<<#x1<<": "< P2; void solve() { INT(n); vvc g(n); int cma = 0; otera::Compressor cmp; vc es; rep(i, n - 1) { INT(a, b, c); -- a, -- b; g[a].eb(b); g[b].eb(a); es.eb(c, P{a, b}); chmax(cma, c); cmp.add(c); } cmp.build(); int sz = si(cmp); vvc

h(sz); rep(i, n - 1) { int a = es[i].sc.fr, b = es[i].sc.sc; int c = es[i].fr; int cid = cmp.get(c); h[cid].eb(a, b); } atcoder::dsu uf(n); otera::LCA lca(g); int ans = cma; vc deg(n); bool check = 1; vc cnt(n, 0); int pre = 0; per(i, sz) { int c = cmp[i]; for(auto [a, b]: h[i]) { int sum = cnt[uf.leader(a)] + cnt[uf.leader(b)]; uf.merge(a, b); cnt[uf.leader(a)] = sum; if(deg[a] >= 2 or deg[b] >= 2) check = 0; if(check and pre == sum) { chmin(ans, (i == 0 ? cma - c : max(cma - c, cmp[i - 1]))); } } for(auto [a, b]: h[i]) { deg[a] ++, deg[b] ++; cnt[uf.leader(a)] ++; if(deg[a] >= 3 or deg[b] >= 3) check = 0; ++ pre; } } out(ans); } signed main() { ios::sync_with_stdio(false); cin.tie(0); // cout << fixed << setprecision(20); // INT(t); rep(i, t)solve(); solve(); return 0; }