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Set SZ as the subtree size, the root depth is 1.

Obviously the answer is min (Dep[p]-1, k) * (Sz[p]-1) + sigma (Sz[u], u in sub-tree of P, Dep[u]-dep[p] <= k)

For the right side of the plus sign, the two-interval constraint asks for information, which can be considered to persist the segment tree, but the information between different versions must satisfy the interval subtraction.

Specifically, the DFS sequence is outside or deep in the outside no matter (depth maximum <=n, so with the depth constant will be small?) ）

1#include <cstdio>2#include <cstdlib>3#include <algorithm>4#include <iostream>5#include <cstring>6#include <string>7 8 using namespacestd;9 Ten voidSetio (Const string&a) { OneFreopen ((A +". in"). C_STR (),"R", stdin); AFreopen ((A +". out"). C_STR (),"W", stdout); - } -  thetypedefLong LongLL; - Const intN =300000+Ten, Logn = -; -  - structNode *pis, *NULL; +  - structNode { + LL S; Anode* ch[2]; at      -Node (LL s =0): s (s) { -ch[0] = ch[1] =NULL; -     } -      -     void*operator New(size_t) { in         returnpis++; -     } to}*root[n], Pool[n *Logn]; +  - #defineMid (L + ((r-l) >> 1)) the #defineLS x->ch[0], y->ch[0], L, mid * #defineRS x->ch[1], y->ch[1], mid + 1, r $ Panax Notoginseng voidBuild (node*& x, Node *y,intLintRintKeyintval) { -x =NewNode (*y), x->s + =Val; the     if(L = = r)return; +     if(Key <= mid) build (LS, key, Val);ElseBuild (RS, Key, Val); A } the  +LL Query (node *x, node *y,intLintRintLfTintRGT) { -     if(LfT <= l && R <= RGT)returnY->s-x->s; $LL res =0; $     if(LfT <= mid) res + =query (LS, LFT, RGT); -     if(Mid < RGT) Res + =query (RS, LFT, RGT); -     returnRes; the } - Wuyi #undefMid the #undefLs - #undefRs Wu  - intDfs_seq[n], pre[n], end[n], sz[n], dep[n], DFS_CLK, MAX_DEP; About  $#include <vector> -vector<int>G[n]; - voidAddedge (intUintv) { - G[u].push_back (v); A g[v].push_back (u); + } the  - voidDfsintu) { $MAX_DEP =Max (MAX_DEP, Dep[u]); theDFS_SEQ[++DFS_CLK] =u; thePre[u] =DFS_CLK; theSz[u] =1; the      for(Unsigned i =0; I < g[u].size (); ++i) { -         intv =G[u][i]; in         if(Dep[v])Continue; theDEP[V] = Dep[u] +1; the Dfs (v); AboutSz[u] + =Sz[v]; the     } theEnd[u] =DFS_CLK; the } +  - intMain () { the #ifdef DEBUGBayiFreopen ("In.txt","R", stdin); theFreopen ("OUT.txt","W", stdout); the #endif -      -PiS =Pool; the     intN, M; thescanf"%d%d", &n, &m); the      for(inti =1; I < n; i++) { the         intu, v; -scanf"%d%d", &u, &v); the Addedge (U, v); the     } the     94dep[1] =1, DFS (1); the      the //cerr << max_dep << Endl; the     98root[0] =NULL=NewNode (0); About     NULL->ch[0] =NULL->ch[1] =NULL; -     101      for(inti =1; I <= N; i++) {102Build (Root[i], root[i-1],1, MAX_DEP, Dep[dfs_seq[i]], Sz[dfs_seq[i]-1);103     }104      the      for(inti =1; I <= m; i++) {106         intp, K;107scanf"%d%d", &p, &k);108ll res = (ll) min (Dep[p]-1, k) * (Sz[p]-1);109Res + = query (Root[pre[p], root[end[p]],1, MAX_DEP, Dep[p] +1, Min (Dep[p] +K, MAX_DEP)); theprintf"%lld\n", res);111     } the     113     return 0; the}

bzoj3653: Laughing