[模板] 树状数组 (C++ class)

闲来无事（其实是打了两三道树状数组题），写了个树状数组模板……

 /*
     Author: hotwords
 */

 template<typename tp>
 class BinTree {
     private:
         int n;tp *a;
     public:
         inline int lowbit(int x)const{return x&-x;}
         int size()const{return n;}
         void empty() {
             if(a) delete []a;
             n=;a=;
         }
         void clear() {
             for(int i=;i<=n;++i) a[i]=;
         }
         void init(int w) {
             empty();
             n=w;
             if(n) {
                 a=new tp[n+];
                 clear();
             }
         }
         void add(int x,tp y) {
             for(;x<=n;x+=lowbit(x)) a[x]+=y;
         }
         tp query(int x) const {
             tp ans=;
             for(;x;x-=lowbit(x)) ans+=a[x];
             return ans;
         }
         tp query(int l,int r) const {
             return query(r)-query(l-);
         }
         BinTree(){n=;a=;}
         ~BinTree(){empty();}
 };

[模板] 树状数组