C++-POJ3321-Apple Tree[数据结构][树状数组]

树上的单点修改+子树查询

用dfn[u]和num[u]可以把任意子树表示成一段连续区间，此时结合树状数组就好了

#include <set>
#include <map>
#include <cmath>
#include <queue>
#include <vector>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;
const int MAXN=(int)1e5+1;
const int MAXM=(int)2e5+1;
int a[MAXN],n,m;char s[5];
int lb(int i){return i&-i;}//lowbit
void add(int i,int v){for(;i<=n;a[i]+=v,i+=lb(i));}
int sum(int i){int ans=0;for(;i;ans+=a[i],i-=lb(i));return ans;}
int query(int i,int j){return sum(j)-sum(i-1);}

struct node{int v,next;}edge[MAXM];
int head[MAXN],cnt;
void addedge(int u,int v){edge[++cnt].v=v,edge[cnt].next=head[u],head[u]=cnt;}
void Addedge(int u,int v){addedge(u,v),addedge(v,u);}

int dfn[MAXN],num[MAXN],index;
void dfs(int u,int fa){
    dfn[u]=++index;
    for(int i=head[u];i;i=edge[i].next){
        int v=edge[i].v;
        if(v!=fa)num[u]++,dfs(v,u),num[u]+=num[v];
    }
}

void Order_C(int x){query(dfn[x],dfn[x])?add(dfn[x],-1):add(dfn[x],1);}
void Order_Q(int x){printf("%d
",query(dfn[x],dfn[x]+num[x]));}

int main() {
    scanf("%d",&n);
    for(int i=1,u,v;i<n;i++)scanf("%d%d",&u,&v),Addedge(u,v);
    dfs(1,1),scanf("%d",&m);
    for(int i=1;i<=n;i++)add(i,1);
    for(int i=1,x;i<=m;i++)scanf("%s%d",s,&x),s[0]=='C'?Order_C(x):Order_Q(x);
    return 0;
}