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Infinite_S

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Jul 16th, 2018
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  1. //In the name of ALLAH
  2.  
  3. #include<bits/stdc++.h>
  4. using namespace std;
  5.  
  6. typedef long long ll;
  7. typedef vector<int> vi;
  8. typedef vector<ll> vl;
  9. typedef vector<vi> vvi;
  10. typedef vector<vl> vvl;
  11. typedef pair<int,int> pii;
  12. typedef pair<double, double> pdd;
  13. typedef pair<ll, ll> pll;
  14. typedef vector<pii> vii;
  15. typedef vector<pll> vll;
  16. typedef double dl;
  17.  
  18. #define PB push_back
  19. //#define PB emplace_back
  20. #define F first
  21. #define S second
  22. #define MP make_pair
  23. #define endl '\n'
  24. #define all(a) (a).begin(),(a).end()
  25. #define sz(x) (int)x.size()
  26. #define mid(l,r) ((r+l)/2)
  27. #define left(node) (node*2)
  28. #define right(node) (node*2+1)
  29. #define mx_int_prime 999999937
  30.  
  31. const double PI = acos(-1);
  32. const double eps = 1e-9;
  33. const int inf = 2000000000;
  34. const ll infLL = 9000000000000000000;
  35. #define MOD 1000000007
  36. //#define harmonic(n) 0.57721566490153286l+log(n)
  37.  
  38. #define mem(a,b) memset(a, b, sizeof(a) )
  39. #define gcd(a,b) __gcd(a,b)
  40. #define sqr(a) ((a) * (a))
  41.  
  42. #define optimize() ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
  43. #define fraction() cout.unsetf(ios::floatfield); cout.precision(10); cout.setf(ios::fixed,ios::floatfield);
  44. #define file() freopen("input.txt","r",stdin);freopen("output.txt","w",stdout);
  45.  
  46. typedef vector<int>::iterator vit;
  47. typedef set<int>::iterator sit;
  48.  
  49. inline bool checkBit(ll n, int i) { return n&(1LL<<i); }
  50. inline ll setBit(ll n, int i) { return n|(1LL<<i); }
  51. inline ll resetBit(ll n, int i) { return n&(~(1LL<<i)); }
  52.  
  53. struct edge {
  54. int u, v, w;
  55. };
  56.  
  57. bool cmp ( const edge &a, const edge &b )
  58. {
  59. return a.w < b.w;
  60. }
  61.  
  62. string to_s(int t)
  63. {
  64. stringstream ss;
  65. ss << t;
  66. return ss.str();
  67. }
  68.  
  69.  
  70. int dx[] = {0, 0, +1, -1};
  71. int dy[] = {+1, -1, 0, 0};
  72. //int dx[] = {+1, 0, -1, 0, +1, +1, -1, -1};
  73. //int dy[] = {0, +1, 0, -1, +1, -1, +1, -1};
  74.  
  75. inline bool EQ(double a, double b) { return fabs(a-b) < 1e-9; }
  76. inline bool isLeapYear(ll year) { return (year%400==0) || (year%4==0 && year%100!=0); }
  77. inline ll lcm ( ll a, ll b ) { return ( a * ( b / gcd (a, b) ) ); }
  78. inline void normal(ll &a) { a %= MOD; (a < 0) && (a += MOD); }
  79. inline ll modMul(ll a, ll b) { a %= MOD, b %= MOD; normal(a), normal(b); return (a*b)%MOD; }
  80. inline ll modAdd(ll a, ll b) { a %= MOD, b %= MOD; normal(a), normal(b); return (a+b)%MOD; }
  81. inline ll modSub(ll a, ll b) { a %= MOD, b %= MOD; normal(a), normal(b); a -= b; normal(a); return a; }
  82. inline ll modPow(ll b, ll p) { ll r = 1; while(p) { if(p&1) r = modMul(r, b); b = modMul(b, b); p >>= 1; } return r; }
  83. inline ll modInverse(ll a) { return modPow(a, MOD-2); }
  84. inline ll modDiv(ll a, ll b) { return modMul(a, modInverse(b)); }
  85.  
  86. /*
  87. bool seive[1010000];
  88. vi prime;
  89.  
  90. void seiveGen(int limit) {
  91. limit += 100;
  92. int sqrtn = sqrt(limit);
  93. for(int i = 3; i <= sqrtn; i += 2) {
  94. if(!seive[i>>1]) {
  95. for(int j = i * i; j < limit; j += i + i) {
  96. seive[j>>1] = 1;
  97. }
  98. }
  99. }
  100. prime.PB(2);
  101. for(int i = 3; i < limit; i += 2) {
  102. if(!seive[i>>1]) prime.PB(i);
  103. }
  104. }
  105. */
  106.  
  107. //
  108. //debug
  109. //#ifdef
  110. template < typename F, typename S >
  111. ostream& operator << ( ostream& os, const pair< F, S > & p ) {
  112. return os << "(" << p.first << ", " << p.second << ")";
  113. }
  114.  
  115. template < typename T >
  116. ostream &operator << ( ostream & os, const vector< T > &v ) {
  117. os << "{";
  118. for(auto it = v.begin(); it != v.end(); ++it) {
  119. if( it != v.begin() ) os << ", ";
  120. os << *it;
  121. }
  122. return os << "}";
  123. }
  124.  
  125. template < typename T >
  126. ostream &operator << ( ostream & os, const set< T > &v ) {
  127. os << "[";
  128. for(auto it = v.begin(); it != v.end(); ++it) {
  129. if( it != v.begin() ) os << ", ";
  130. os << *it;
  131. }
  132. return os << "]";
  133. }
  134.  
  135. template < typename T >
  136. ostream &operator << ( ostream & os, const multiset< T > &v ) {
  137. os << "[";
  138. for(auto it = v.begin(); it != v.end(); ++it) {
  139. if( it != v.begin() ) os << ", ";
  140. os << *it;
  141. }
  142. return os << "]";
  143. }
  144.  
  145. template < typename F, typename S >
  146. ostream &operator << ( ostream & os, const map< F, S > &v ) {
  147. os << "[";
  148. for(auto it = v.begin(); it != v.end(); ++it) {
  149. if( it != v.begin() ) os << ", ";
  150. os << it -> first << " = " << it -> second ;
  151. }
  152. return os << "]";
  153. }
  154.  
  155. #define dbg(args...) do {cerr << #args << " : "; faltu(args); } while(0)
  156.  
  157. clock_t tStart = clock();
  158. #define timeStamp dbg("Execution Time: ", (double)(clock() - tStart)/CLOCKS_PER_SEC)
  159.  
  160. void faltu () {
  161. cerr << endl;
  162. }
  163.  
  164. template <typename T>
  165. void faltu( T a[], int n ) {
  166. for(int i = 0; i < n; ++i) cerr << a[i] << ' ';
  167. cerr << endl;
  168. }
  169.  
  170. template <typename T, typename ... hello>
  171. void faltu( T arg, const hello &... rest) {
  172. cerr << arg << ' ';
  173. faltu(rest...);
  174. }
  175. //#else
  176. //#define dbg(args...)
  177.  
  178. const int mx = 1e5+123;
  179. int p[mx][30], p_mx[mx][30], chainHead[mx], chainInd[mx], chainNo, ptr, basePos[mx],baseArry[mx], parent[mx], level[mx], n, sz[mx];
  180. vii Aj[mx];
  181.  
  182. int dfs ( int u, int lev )
  183. {
  184. level[u] = lev;
  185. sz[u] = 1;
  186. for ( auto v : Aj[u] ) {
  187. if ( parent[u] != v.F ) {
  188. parent[v.F] = u;
  189. sz[u] += dfs ( v.F, lev+1 );
  190. }
  191. }
  192.  
  193. return sz[u];
  194. }
  195.  
  196. void preprocess()
  197. {
  198. for ( int i = 1; i <= n; i++ ) {
  199. p[i][0] = parent[i];
  200. p_mx[i][0] = baseArry[i];
  201. }
  202.  
  203. for ( int j = 1; ( 1 << j ) <= n; j++ ) {
  204. for ( int i = 1; i <= n; i++ ) {
  205. if ( p[i][j-1] != -1 ) p[i][j] = p[p[i][j-1]][j-1];
  206. if ( i+(1<<(j-1)) <= n ) p_mx[i][j] = max ( p_mx[i][j-1], p_mx[i+(1<<(j-1))][j-1] );
  207. }
  208. }
  209. }
  210.  
  211. int query_mx ( int l, int r )
  212. {
  213. int j = log2 ( r - l + 1 );
  214. return max ( p_mx[l][j], p_mx[r-(1<<j)+1][j] );
  215. }
  216.  
  217. int LCA ( int u, int v )
  218. {
  219. if ( level[u] < level[v] ) swap ( u, v );
  220.  
  221. int dist = level[u] - level[v];
  222. while ( dist > 0 ) {
  223. int rise = log2 ( dist );
  224. u = p[u][rise];
  225. dist -= ( 1 << rise );
  226. }
  227.  
  228. if ( u == v ) return u;
  229.  
  230. for ( int i = 20; i >= 0; i-- ) {
  231. if ( p[u][i] != p[v][i] && p[u][i] != -1 ) {
  232. u = p[u][i];
  233. v = p[v][i];
  234. }
  235. }
  236.  
  237. return parent[u];
  238. }
  239.  
  240. void HLD ( int u, int cost )
  241. {
  242. if ( chainHead[chainNo] == -1 ) {
  243. chainHead[chainNo] = u;
  244. }
  245.  
  246. chainInd[u] = chainNo;
  247. basePos[u] = ++ptr;
  248. baseArry[ptr] = cost;
  249.  
  250. int m = -1, id = -1, c = -1;
  251.  
  252. for ( auto v : Aj[u] ) {
  253. if ( sz[v.F] > m && v.F != parent[u] ) {
  254. m = sz[v.F], id = v.F, c = v.S;
  255. }
  256. }
  257.  
  258. if ( id != -1 ) HLD ( id, c );
  259.  
  260. for ( auto v : Aj[u] ) {
  261. if ( parent[u] != v.F && v.F != id ) {
  262. chainNo++;
  263. HLD ( v.F, v.S );
  264. }
  265. }
  266. }
  267.  
  268. int query_up ( int u, int v )
  269. {
  270. int chainU, chainV = chainInd[v], ans = 0;
  271. if ( v == u ) return 0;
  272.  
  273. while ( 1 ) {
  274. chainU = chainInd[u];
  275. if ( chainU == chainV ) {
  276. if ( u == v ) return ans;
  277. ans = max ( ans, query_mx( basePos[v]+1, basePos[u] ) );
  278. return ans;
  279. }
  280.  
  281. ans = max ( ans, query_mx( basePos[chainHead[chainU]], basePos[u] ) );
  282. u = chainHead[chainU];
  283. u = parent[u];
  284. }
  285. }
  286.  
  287. int query ( int u, int v )
  288. {
  289. int lca = LCA ( u, v );
  290. return max ( query_up( u, lca ), query_up( v, lca ) );
  291. }
  292.  
  293. int main()
  294. {
  295. optimize();
  296.  
  297. int t, u, v, w;
  298. while ( cin >> n ) {
  299.  
  300. if ( n == 0 ) break;
  301.  
  302. mem ( chainHead, -1 );
  303. mem ( p, -1 );
  304. ptr = 0, chainNo = 1;
  305.  
  306. for ( int i = 0; i <= 1e5; i++ ) {
  307. Aj[i].clear();
  308. parent[i] = i;
  309. }
  310.  
  311.  
  312. for ( int i = 1; i < n; i++ ) {
  313. cin >> u >> v >> w;
  314. Aj[u].PB ( { v, w } );
  315. Aj[v].PB ( { u, w } );
  316. }
  317.  
  318. dfs ( 1, 0 );
  319. HLD ( 1, -1 );
  320. preprocess();
  321.  
  322. int q;
  323. cin >> q;
  324. while ( q-- ) {
  325. cin >> u >> v;
  326. cout << query( u, v ) << endl;
  327. }
  328.  
  329. }
  330.  
  331. return 0;
  332. }
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