0106.cpp

class Solution {
public:
    TreeNode* postdfs(vector<int>& in, vector<int>& post, TreeNode* stop) {
        
        if ( post.empty() || (stop && in.back() == stop->val) )
            return NULL;
        
        TreeNode* root = new TreeNode(post.back());
        
        post.pop_back();
        
        root -> right = postdfs(in, post, root);
        
        in.pop_back();
        
        root -> left = postdfs(in, post, stop);
        
        return root;
    }
    
    TreeNode* buildTree(vector<int>& inorder, vector<int>& postorder) {
        vector<int> in(inorder), post(postorder);
        
        return postdfs(in, post, (TreeNode*)NULL);
    }
};