[poj 3321]Apple Tree[树状数组]

#include <cstring>
#include <cstdio>
#include <algorithm>
using namespace std;
const int MAXN = 100010;
int n,m;
int head[MAXN],num;
struct pool
{
int v,next;
}g[MAXN];
void add(int u, int v)
{
g[++num].v = v;
g[num].next = head[u];
head[u] = num;
}
inline int lowbit(int x)
{
return x&(-x);
}
int l[MAXN],r[MAXN];
void dfs(int u)
{
l[u] = ++num;
for(int i=head[u];i;i=g[i].next)
{
//printf("i = %d, dfs(%d);\n",i,g[i].v);
dfs(g[i].v);
}
r[u] = num;
}
int a[MAXN],c[MAXN];
int sum(int x)
{
int ans = 0;
for(;x>0;x^=lowbit(x))  ans += c[x];
return ans;
}
void modify(int x, int d)
{
for(;x<=n;x+=lowbit(x)) c[x] += d;
}
int main()
{
scanf("%d",&n);
for(int i=0,v,u;i<n-1;i++)
{
scanf("%d%d",&u,&v);
add(u, v);
}
num = 0;
// printf("&&&");
dfs(1);
// printf("***");
for(int i=1;i<=n;i++)//init
{
a[i] = 1;
c[i] = lowbit(i);
}
scanf("%d",&m);
char s[5];
while(m--)
{
scanf("%s%d",s,&num);
if(s[0]=='C')
{
modify(l[num],a[num]?-1:1);
a[num] ^= 1;
}
else
printf("%d\n",sum(r[num])-sum(l[num]-1));
}
}