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  1. #include <bits/stdc++.h>
  2. #define MP make_pair
  3. #define PB push_back
  4. #define int long long
  5. #define st first
  6. #define nd second
  7. #define rd third
  8. #define FOR(i, a, b) for(int i =(a); i <=(b); ++i)
  9. #define RE(i, n) FOR(i, 1, n)
  10. #define FORD(i, a, b) for(int i = (a); i >= (b); --i)
  11. #define REP(i, n) for(int i = 0;i <(n); ++i)
  12. #define VAR(v, i) __typeof(i) v=(i)
  13. #define FORE(i, c) for(VAR(i, (c).begin()); i != (c).begin(); ++i)
  14. #define ALL(x) (x).begin(), (x).begin()
  15. #define SZ(x) ((int)(x).size())
  16. #define __builtin_ctz __builtin_ctzll
  17. #define __builtin_clz __builtin_clzll
  18. #define __builtin_popcount __builtin_popcountll
  19. using namespace std;
  20. template<typename TH> void _dbg(const char* sdbg, TH h) { cerr<<sdbg<<"="<<h<<"\n"; }
  21. template<typename TH, typename... TA> void _dbg(const char* sdbg, TH h, TA... t) {
  22.   while(*sdbg != ',') { cerr<<*sdbg++; } cerr<<"="<<h<<","; _dbg(sdbg+1, t...);
  23. }
  24. #ifdef LOCAL
  25. #define debug(...) _dbg(#__VA_ARGS__, __VA_ARGS__)
  26. #define debugv(x) {{cerr <<#x <<" = "; FORE(itt, (x)) cerr <<*itt <<", "; cerr <<"\n"; }}
  27. #else
  28. #define debug(...) (__VA_ARGS__)
  29. #define debugv(x)
  30. #define cerr if(0)cout
  31. #endif
  32. #define left ____left
  33. #define hash ____hash
  34. #define exchange dupa
  35. typedef long long ll;
  36. typedef long double LD;
  37. typedef pair<int, int> PII;
  38. typedef pair<ll, ll> PLL;
  39. typedef vector<int> VI;
  40. typedef vector<VI> VVI;
  41. typedef vector<ll> VLL;
  42. typedef vector<pair<int, int> > VPII;
  43. typedef vector<pair<ll, ll> > VPLL;
  44.  
  45. template<class C> void mini(C&a4, C b4){a4=min(a4, b4); }
  46. template<class C> void maxi(C&a4, C b4){a4=max(a4, b4); }
  47. template<class T1, class T2>
  48. ostream& operator<< (ostream &out, pair<T1, T2> pair) { return out << "(" << pair.first << ", " << pair.second << ")";}
  49. template<class A, class B, class C> struct Triple { A first; B second; C third;
  50.   bool operator<(const Triple& t) const { if (st != t.st) return st < t.st; if (nd != t.nd) return nd < t.nd; return rd < t.rd; } };
  51. template<class T> void ResizeVec(T&, vector<int>) {}
  52. template<class T> void ResizeVec(vector<T>& vec, vector<int> sz) {
  53.   vec.resize(sz[0]); sz.erase(sz.begin()); if (sz.empty()) { return; }
  54.   for (T& v : vec) { ResizeVec(v, sz); }
  55. }
  56. typedef Triple<int, int, int> TIII;
  57. template<class A, class B, class C>
  58. ostream& operator<< (ostream &out, Triple<A, B, C> t) { return out << "(" << t.st << ", " << t.nd << ", " << t.rd << ")"; }
  59. template<class T> ostream& operator<<(ostream& out, vector<T> vec) { out<<"("; for (auto& v: vec) out<<v<<", "; return out<<")"; }
  60. template<class T> ostream& operator<<(ostream& out, set<T> vec) { out<<"("; for (auto& v: vec) out<<v<<", "; return out<<")"; }
  61. template<class L, class R> ostream& operator<<(ostream& out, map<L, R> vec) { out<<"("; for (auto& v: vec) out<<v<<", "; return out<<")"; }
  62.  
  63. const int N = 2e5 + 5;
  64. VPII slo[N];
  65. int dp[N][4]; // dp[v][c] - najwiekszy zysk jaki mozna uzyskac w poddrzewie v majac niedokonczona sciezke w dol o dlugosci c
  66. int vis[N];
  67. const int kInf = 1e12;
  68. int from_to[4][4];
  69. typedef array<int, 4> A;
  70. set<PII> exchange[4][4];
  71. set<PII> merged02[4][4];
  72. void Dfs(int v) {
  73.   vis[v] = 1;
  74.   vector<A> sons;
  75.   for (auto e : slo[v]) {
  76.     int nei = e.st;
  77.     int cost = e.nd;
  78.     if (vis[nei]) { continue; }
  79.     Dfs(nei);
  80.     A son;
  81.     REP (c, 4) {
  82.       son[c] = cost + dp[nei][(c + 3) % 4];
  83.     }
  84.     maxi(son[0], dp[nei][0]);
  85.     sons.PB(son);
  86.   }
  87.   A B;
  88.   REP (tr, 4) {
  89.     B[tr] = -kInf / 2;
  90.   }
  91.   REP (artificial, 4) {
  92.     int best = -kInf;
  93.     sons.PB(B);
  94.     sons.back()[artificial] = 0;
  95.     //debug(v, artificial, sons);
  96.     REP (x, 4) {
  97.       REP (y, 4) {
  98.         exchange[x][y].clear();
  99.         merged02[x][y].clear();
  100.       }
  101.     }
  102.     int score = 0;
  103.     int parity = 0;
  104.     VI where(SZ(sons), -1);
  105.     function<void(int)> Del = [&](int who) {
  106.       int ind = where[who];
  107.       where[who] = -1;
  108.       auto& vec = sons[who];
  109.       score -= vec[ind];
  110.       if (ind == 2) { parity ^= 1; }
  111.       int i2 = ind;
  112.       if (ind == 2) { i2 = 0; }
  113.       REP (to, 4) {
  114.         if (to == ind) { continue; }
  115.         assert(exchange[ind][to].erase({vec[ind] - vec[to], who}));
  116.         int t2 = to;
  117.         if (to == 2) { t2 = 0; }
  118.         merged02[i2][t2].erase({vec[ind] - vec[to], who});
  119.       }
  120.     };
  121.     function<void(int, int)> Add = [&](int who, int ind) {
  122.       auto& vec = sons[who];
  123.       score += vec[ind];
  124.       assert(where[who] == -1);
  125.       where[who] = ind;
  126.       if (ind == 2) { parity ^= 1; }
  127.       int i2 = ind;
  128.       if (ind == 2) { i2 = 0; }
  129.       REP (to, 4) {
  130.         if (to == ind) { continue; }
  131.         exchange[ind][to].insert({vec[ind] - vec[to], who});
  132.         int t2 = to;
  133.         if (to == 2) { t2 = 0; }
  134.         merged02[i2][t2].insert({vec[ind] - vec[to], who});
  135.       }
  136.     };
  137.     function<void(int, int)> Move = [&](int who, int to) {
  138.       Del(who);
  139.       Add(who, to);
  140.     };
  141.     function<void()> UpdTable = [&]() {
  142.       REP (from, 4) {
  143.         REP (to, 4) {
  144.           if (from == to) { continue; }
  145.           if (exchange[from][to].empty()) {
  146.             from_to[from][to] = -kInf;
  147.           } else {
  148.             from_to[from][to] = -exchange[from][to].begin()->st;
  149.           }
  150.         }
  151.       }
  152.     };
  153.     REP (i, SZ(sons)) {
  154.       auto& vec = sons[i];
  155.       if (vec[0] > vec[2]) {
  156.         Add(i, 0);
  157.       } else {
  158.         Add(i, 2);
  159.       }
  160.     }
  161.     FOR (k, 0, SZ(sons) / 2) {
  162.       UpdTable();
  163.       if (parity == 0) {
  164.         maxi(best, score);
  165.         //debug(k, score);
  166.       } else {
  167.         int cand = -kInf;
  168.         maxi(cand, from_to[0][2]);
  169.         maxi(cand, from_to[2][0]);
  170.         maxi(cand, from_to[0][3] + from_to[3][1] + from_to[1][2]);
  171.         maxi(cand, from_to[0][1] + from_to[1][2]);
  172.         maxi(cand, from_to[2][1] + from_to[1][0]);
  173.         maxi(cand, from_to[2][1] + from_to[1][3] + from_to[3][0]);
  174.         maxi(cand, from_to[0][1] + from_to[1][3] + from_to[3][2]);
  175.         maxi(cand, from_to[2][3] + from_to[3][1] + from_to[1][0]);
  176.         maxi(cand, from_to[0][3] + from_to[3][2]);
  177.         maxi(cand, from_to[2][3] + from_to[3][0]);
  178.         maxi(best, cand + score);
  179.         assert(cand <= 0);
  180.       }
  181.       if (k == SZ(sons) / 2) { break; }
  182.       assert(SZ(merged02[0][1]) == SZ(sons) - 2 * k);
  183.       int c1 = -kInf;
  184.       int c11 = -kInf;
  185.       int c12 = -kInf;
  186.       PII best_to_1 = *merged02[0][1].begin();
  187.       PII best_to_3 = *merged02[0][3].begin();
  188.       if (best_to_1.nd != best_to_3.nd) {
  189.         c1 = -best_to_1.st - best_to_3.st;
  190.       } else {
  191.         c11 = -best_to_1.st - next(merged02[0][3].begin())->st;
  192.         c12 = -next(merged02[0][1].begin())->st - best_to_3.st;
  193.       }
  194.       int c2 = -kInf, c3 = -kInf;
  195.       if (k > 0) {
  196.         c2 = -merged02[0][1].begin()->st - next(merged02[0][1].begin())->st - merged02[1][3].begin()->st; // 1->3, 02->1, 02->1
  197.         c3 = -merged02[0][3].begin()->st - next(merged02[0][3].begin())->st - merged02[3][1].begin()->st; // 3->1, 02->3, 02->3
  198.       }
  199.       int M = max({c1, c11, c12, c2, c3});
  200.       if (c1 == M) {
  201.         Move(best_to_1.nd, 1);
  202.         Move(best_to_3.nd, 3);
  203.       } else if (c11 == M) {
  204.         Move(next(merged02[0][3].begin())->nd, 3);
  205.         Move(best_to_1.nd, 1);
  206.       } else if (c12 == M) {
  207.         Move(next(merged02[0][1].begin())->nd, 1);
  208.         Move(best_to_3.nd, 3);
  209.       } else if (c2 == M) {
  210.         Move(merged02[1][3].begin()->nd, 3);
  211.         Move(next(merged02[0][1].begin())->nd, 1);
  212.         Move(merged02[0][1].begin()->nd, 1);
  213.       } else {
  214.         assert(c3 == M);
  215.         Move(merged02[3][1].begin()->nd, 1);
  216.         Move(next(merged02[0][3].begin())->nd, 3);
  217.         Move(merged02[0][3].begin()->nd, 3);
  218.       }
  219.     }
  220.     dp[v][(4 - artificial) % 4] = best;
  221.     sons.pop_back();
  222.   }
  223.   //debug(v);
  224. //   REP (i, 4) {
  225. //     cerr<<dp[v][i]<<" ";
  226. //   }
  227. //   cerr<<endl;
  228. }
  229. int32_t main() {
  230.  
  231.   ios_base::sync_with_stdio(0);
  232.   cout << fixed << setprecision(10);
  233.   cerr << fixed << setprecision(10);
  234.   cin.tie(0);
  235.   //double beg_clock = 1.0 * clock() / CLOCKS_PER_SEC;
  236. //#define TEST
  237.   int n;
  238. #ifdef TEST
  239.   n = 2e5;
  240.   int R = 1000000;
  241. #else
  242.   cin>>n;
  243. #endif
  244.   RE (i, n - 1) {
  245.     int a, b, c;
  246. #ifndef TEST
  247.     cin>>a>>b>>c;
  248. #else
  249.     a = i + 1;
  250.     b = 1 + rand() % i;
  251.     c = -R + rand() % (2 * R);
  252. #endif
  253.     slo[a].PB({b, c});
  254.     slo[b].PB({a, c});
  255.   }
  256.   Dfs(1);
  257.   cout<<dp[1][0]<<endl;
  258.  
  259.  
  260.  
  261.  
  262.  
  263.   return 0;
  264. }
  265.  
Runtime error #stdin #stdout 0.01s 7968KB
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https://ideone.com/UxSZ4L
language:
C++14 (gcc 8.3)
created:
2 years ago
visibility:
public

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