POJ3321 Apple tree

/*
    很容易发现这题用线段树来做
树形结构稍微处理一下就可以变为线性结构，dfs跑一遍将树中的结点重新编号，对于每个节点，当访问完子树之后，将子树的最大节点也保存，这样就能得到一个区间段，于是乎，每棵子树的编号就都变成连续的（读入时的标号与线段树中实际标号不一样，所以先用一个pre数组来记录原来的标号），剩下的就可以套用线段树或者是树状数组的模板了，当查询某个结点时查询所对应的连续区间就可以了
*/

#include<iostream>
#include<cstdio>
#include<algorithm> 
#include<cstring> 
using namespace std; 
#define maxn 100010
struct node{ 
    int lef, rig, id;
}tree[maxn];
int root[maxn];
int n, q, v; 
struct E{
    int v, next; 
}edge[maxn]; 
int pre[maxn], apple[maxn];
struct SEG{ 
    int lef, rig, mid, ans; 
}seg[maxn*4];  
void dfs(int pp)
{
    tree[pp].lef = v; 
    for(int i= pre[pp]; i!= -1; i= edge[i].next)
      dfs(edge[i].v);
    root[pp] = v; tree[pp].rig = v++; 
} 
void maketree(int num, int lef, int rig)
{ 
    seg[num].lef = lef; 
    seg[num].rig = rig; 
    seg[num].mid = (lef + rig) >> 1; 
    seg[num].ans = rig - lef + 1; 
    if( lef != rig)
    { 
        maketree(num*2, lef, seg[num].mid); 
        maketree(num*2+1, seg[num].mid+1, rig); 
    } 
} 
int cal( int num, int lef, int rig)
{ 
    if( seg[num].lef == lef && seg[num].rig == rig)
      return seg[num].ans; 
      if( rig <= seg[num].mid)
        return cal( num*2, lef, rig); 
      else if( lef > seg[num].mid)
        return cal( num*2+1 , lef, rig);
      else return cal( num*2, lef , seg[num].mid) + cal(num*2+1, seg[num].mid+1, rig); 
} 
void insert( int num, int lef, int val)
{ 
    seg[num].ans += val; 
    if( seg[num].lef == seg[num].rig) 
      return; 
    if( lef <= seg[num].mid) 
      insert( num*2, lef, val); 
    else if( lef > seg[num].mid) 
      insert( num*2+1, lef, val); 
}
void init() 
{ 
    int aa, bb, value = 0; 
    memset( pre, -1, sizeof(pre)); 
    for(int i= 1; i<n; i++) 
    { 
        scanf("%d%d", &aa, &bb); 
        edge[value].v = bb; 
        edge[value].next = pre[aa];  
        pre[aa] = value++; 
    } 
    for(int i= 1; i<= n; i++) 
      apple[i] = 1; 
}
int main() 
{ 
    int aa, bb; 
    char tmp[10]; 
    scanf("%d", &n); 
    init(); 
    v = 1; 
    dfs(1); 
    maketree(1, 1, n); 
    scanf("%d", &q); 
    for(int i= 0; i<q; i++) 
    { 
        scanf("%s%d", tmp, &aa); 
        if( tmp[0] == 'Q') 
          printf("%d\n", cal(1, tree[aa].lef, tree[aa].rig)); 
        else 
        { 
            if( apple[root[aa]] == 1) 
            bb = -1; 
            else bb = 1; 
            insert( 1, root[aa], bb); 
            apple[root[aa]] = 1 - apple[root[aa]]; 
        } 
    }
    return 0; 
}