【模板】树状数组

//          可引入二维！！！！  </span>int n;int tree[MAXN]; inline int lowbit(int x){return x&(-x);}int add(int a,int v){   for(int i=x;i<=n;i+=lowbit(i))    tree[i]+=v;}[ SUM(a,b)=sum(b)-sum(a); ][ sum(x); ]int sum(int x){  int ans=0;  for(int i=x;i;i-=lowbit(i))    ans+=tree[i];  return ans;}