剑指offer：二叉搜索树的后序遍历序列

class Solution {
public:
bool VerifySquenceOfBST(vector<int> sequence) {

if(sequence.size()==0){
return false;
}

return helper(sequence, 0, sequence.size() - 1);
}

private:
bool helper(vector<int> &sequence, int left, int right){

if(left==right){
return true;
}

int root = sequence[right];

int i = left;

for (; i <= right - 1; i++){
if (sequence[i]>root){
break;
}
}

int j = i;

for (; j <= right - 1; j++){
if (sequence[j]<root){
return false;
}
}

bool le =true;

if (i - 1>=left){
le = helper(sequence, left, i - 1);
}

bool ri =true;

if (i<=right - 1){
ri = helper(sequence, i, right - 1);
}

return le && ri;
}

};