POJ 3321 Apple tree (+dfs sequence)

Title Link: http://poj.org/problem?id=3321

Give you n points, n-1, 1 is the root node. For you m operation, the C operation is to reverse the X point (1 to 0,0 to 1), and the Q operation is to ask for the sum of the X node and the value of its subtree. The initial all nodes are 1.

The DFS-ordered method will iterate through all nodes with 1 as the root node, L[i] represents the earliest timestamp that occurs at point I, R[i] represents the latest timestamp of the I point, and two occurrences per node.

So if you query the sum of the values of I and its subtree, simply query the value between L[i]~r[i] in the tree array and divide by 2, the complexity of log (n). If you change the operation, just change the value on the subscript l[i] and r[i].

Similar topics are HDU3974, but the segment tree is updated and is also written using the Dfs sequence method.

1#include <iostream>2#include <cstring>3#include <cstdio>4#include <vector>5 using namespacestd;6 Const intMAXN = 2e5 +5;7 Const intINF =1e9;8 intHEAD[MAXN], N, M, CNT, L[MAXN], R[MAXN], BIT[MAXN *2], DFN, A[MAXN];9 //a array represents the value of each elementTen structData { One     intnext, to; A}EDGE[MAXN *2]; -  -InlinevoidAdd_edge (intW Nintv) { theEdge[cnt].next =Head[u]; -Edge[cnt].to =v; -Head[u] = cnt++; - } +  - voidDfsintW Nintpar) { +L[u] = + +DFN; A      for(inti = Head[u]; ~i; i =Edge[i].next) { at         intv =edge[i].to; -         if(v = =par) -             Continue; - Dfs (v, u); -     } -R[u] = + +DFN; in } -  toInlinevoidAddintIintx) { +      for(; I <= dfn; i + = (I &-i)) -Bit[i] + =x; the } *  $ intSuminti) {Panax Notoginseng     ints =0; -      for(; I >=1; I-= (I &-i)) thes + =Bit[i]; +     returns; A } the  + intMain () - { $     intu, v; $     Charq[5]; -      while(~SCANF ("%d", &N)) { -Memset (Head,-1,sizeof(head)); thememset (bit,0,sizeof(bit)); -Memset (A,0,sizeof(a));WuyiCNT = DFN =0; the          for(inti =1; I < n; i++) { -scanf"%d%d", &u, &v); Wu Add_edge (U, v); - Add_edge (V, u); About         } $Dfs1, -1); -scanf"%d", &m); -          while(m--) { -scanf"%s%d", Q, &u); A             if(q[0] =='Q') { +printf"%d\n", ((R[u]-l[u] +1)-(SUM (r[u])-sum (L[u]-1))) /2);//except 2 because each point in the DFS sequence appears 2 times the             } -             Else { $                 if(A[u]) { theAdd (L[u],-1); theAdd (R[u],-1); theA[u] =0; the                 } -                 Else { inAdd (L[u],1); theAdd (R[u],1); theA[u] =1; About                 } the             } the         } the     } +}

POJ 3321 Apple tree (+dfs sequence)