class Solution {
public:
    bool verifyPostorder(vector<int>& postorder) {
        stack<int> s;
        int root = INT_MAX;

        for(int i=postorder.size()-1;i>=0;i--)
        {
            if(postorder[i] > root)
            return false;
            while(!s.empty() && s.top() > postorder[i])
            {
                root = s.top();
                s.pop();
            }
            s.push(postorder[i]);
        }

        return true;
    }
};