二叉搜索树的后序遍历序列

class Solution {
public:
    bool isBST(vector<int> &s,int a,int b)
        {
        if(b<a)
            return false;
        if(b==a)
            return true;
        int root=s[b];
        int i,j;
        for(i=a;i<=b-1;i++)
         if(s[i]>root)break;
        bool  left=true;
        if(i>a)
         left=isBST(s,a,i-1);
        for(j=i;j<=b-1;j++)
            if(s[j]<root)return false;
        bool right=true;
        if(i<b-1) return isBST(s,i,b-1);
        return left&&right;
        
    }
    bool VerifySquenceOfBST(vector<int> sequence) {
       if(sequence.size()<0||sequence.size()==0)
           return false;
        if(sequence.size()==1)
            return true;
        int len=sequence.size();
        return isBST(sequence,0,len-1);
        
    }
};