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  1. /*
  2. * @Author: hungeazy
  3. * @Date:   2024-08-08 14:21:44
  4. * @Last Modified by:   hungeazy
  5. * @Last Modified time: 2024-08-08 15:25:02
  6. */
  7. #include <bits/stdc++.h>
  8. // #pragma GCC optimize("O3")  
  9. // #pragma GCC optimize("unroll-loops")  
  10. // #pragma GCC target("avx2,bmi,bmi2,popcnt,lzcnt")  
  11. using namespace std;
  12. #define fast ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
  13. #define int long long
  14. #define ull unsigned long long
  15. #define sz(x) x.size()
  16. #define sqr(x) (1LL * (x) * (x))
  17. #define all(x) x.begin(), x.end()
  18. #define fill(f,x) memset(f,x,sizeof(f))
  19. #define FOR(i,l,r) for(int i=l;i<=r;i++)
  20. #define FOD(i,r,l) for(int i=r;i>=l;i--)
  21. #define ii pair<int,int>
  22. #define iii pair<int,ii>
  23. #define di pair<ii,ii>
  24. #define vi vector<int>
  25. #define vii vector<ii>
  26. #define mii map<int,int>
  27. #define fi first
  28. #define se second
  29. #define pb push_back
  30. #define MOD 1000000007
  31. #define __lcm(a,b) (1ll * ((a) / __gcd((a), (b))) * (b))
  32. #define YES cout << "YES\n"
  33. #define NO cout << "NO\n"
  34. #define MASK(i) (1LL << (i))
  35. #define c_bit(i) __builtin_popcountll(i)
  36. #define BIT(x,i) ((x) & MASK(i))
  37. #define SET_ON(x,i) ((x) | MASK(i))
  38. #define SET_OFF(x,i) ((x) & ~MASK(i))
  39. #define oo 1e18
  40. #define name ""
  41. #define endl '\n'
  42. #define time() cerr << endl << "-------------Time:" << 1000.0 * clock() / CLOCKS_PER_SEC << "ms.";
  43. template<typename T> bool maximize(T &res, const T &val) { if (res < val){ res = val; return true; }; return false; }
  44. template<typename T> bool minimize(T &res, const T &val) { if (res > val){ res = val; return true; }; return false; }
  45. const int N = (int)1e5+10;
  46. int n,q;
  47. vii g[N];
  48.  
  49. namespace hungeazy {
  50.  
  51. 	int ma[N][20],h[N],par[N][20];
  52.  
  53. 	void DFS(int u, int p)
  54. 	{
  55. 		for (ii x : g[u])
  56. 			if (x.fi != p)
  57. 			{
  58. 				h[x.fi] = h[u]+1;
  59. 				ma[x.fi][0] = x.se;
  60. 				par[x.fi][0] = u;
  61. 				DFS(x.fi,u);
  62. 			}
  63. 	}
  64.  
  65. 	void init()
  66. 	{
  67. 		FOR(j,1,log2(n))
  68. 			FOR(i,1,n) ma[i][j] = max(ma[i][j-1],ma[par[i][j-1]][j-1]), par[i][j] = par[par[i][j-1]][j-1];
  69. 	}
  70.  
  71. 	int LCA(int x, int y)
  72. 	{
  73. 		if (h[x] < h[y]) swap(x,y);
  74. 		int z = log2(n), ans = -oo;
  75. 		FOD(i,z,0)
  76. 			if (h[x]-h[y] >= MASK(i)) ans = max(ans,ma[x][i]), x = par[x][i];
  77. 		if (x == y) return ans;
  78. 		FOD(i,z,0)
  79. 			if (par[x][i] != par[y][i]) ans = max({ans,ma[x][i],ma[y][i]}), x = par[x][i], y = par[y][i];
  80. 		ans = max({ans,ma[x][0],ma[y][0]});
  81. 		return ans;
  82. 	}
  83.  
  84. 	void solve(void)
  85. 	{
  86. 		DFS(1,-1);
  87. 		init();
  88. 		while (q--)
  89. 		{
  90. 			int u,v;
  91. 			cin >> u >> v;
  92. 			cout << LCA(u,v) << endl;
  93. 		}
  94. 	}
  95.  
  96. }
  97.  
  98. signed main()
  99. {
  100.     fast;
  101.     if (fopen(name".inp","r"))
  102.     {
  103.     	freopen(name".inp","r",stdin);
  104.     	freopen(name".out","w",stdout);
  105.     }
  106.     cin >> n >> q;
  107.     FOR(i,1,n-1)
  108.     {
  109.     	int u,v,w;
  110.     	cin >> u >> v >> w;
  111.     	g[u].pb({v,w}); g[v].pb({u,w});
  112.     }
  113.     hungeazy::solve();
  114.     time();
  115.     return 0;
  116. }
Success #stdin #stdout #stderr 0.01s 6680KB
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-------------Time:6.744ms.
https://ideone.com/u0MfMx
language:
C++14 (gcc 8.3)
created:
8 hours ago
visibility:
public

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