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(利用树状数组统计子树权和8.3.1)POJ 3321 Apple Tree(利用树状数组动态统计子树权和)


/*
 * POJ_3321.cpp
 *
 *  Created on: 2013年11月5日
 *      Author: Administrator
 */

#include <iostream>
#include <cstdio>
#include <cstring>

using namespace std;

const int maxn = 100010;

struct node1{
	int next;//下一条边的序号为edge[i].next
	int tail;//与dii条边相连的节点为edge[i].tail
}edge[maxn];

struct node2{//第i个节点为根的子树在后根序列中的区间为[apple[i].l,apple[i].r];
	int l;
	int r;
}apple[maxn];

/**
 * a[i]: 第ige节点的权值
 * cnt: 后跟序列中的序号
 * s[i]: 第i条边的序号
 * c[]: 树状数组
 */
int a[maxn],cnt,s[maxn],c[maxn];

void DFS(int u){//从节点u出发计算以每个节点为根节点的子树区间[apple[i].l,apple[i].r]
	apple[u].l = cnt;

	int i;
	for(i = s[u]; i != -1 ; i = edge[i].next){
		DFS(edge[i].tail);
	}
	apple[u].r = cnt++;
}

int lowbit(int x){
	return x&(-x);
}

void change(int x){//从a[x]出发调整树状数组
	int i;
	if(a[x]){
		for(i = x ; i < cnt ; i += lowbit(i)){
			c[i]++;
		}
	}else{
		for(i = x ; i < cnt ; i += lowbit(i)){
			c[i]--;
		}
	}
}

int sum(int x){//计算a[1]....a[k]的和
	int i;
	int res = 0;
	for(i = x ; i > 0 ; i -= lowbit(i)){
		res += c[i];
	}

	return res;
}

int main(){
	int i,n,m,t1,t2,t;
	char str[3];
	scanf("%d",&n);
	memset(s,-1,sizeof(s[0])*(n+1));
	memset(c,0,sizeof(c[0])*(n+1));
	memset(apple,0,sizeof(apple[0])*(n+1));
	for(i = 0 ; i < n-1 ; ++i){
		scanf("%d%d",&t1,&t2);
		edge[i].tail = t2;
		edge[i].next = s[t1];
		s[t1] = i;
	}

	cnt = 1;
	DFS(1);

	scanf("%d",&m);
	for(i = 1 ; i <= n ; ++i){
		a[i] = 1;
		change(i);
	}

	while(m--){
		scanf("%s%d",str,&t);
		if(str[0] == 'Q'){
			printf("%d\n",sum(apple[t].r) - sum(apple[t].l - 1));
		}else{
			a[apple[t].r] = (a[apple[t].r] + 1)%2;
			change(apple[t].r);
		}
	}

	return 0;
}


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