LINTCODE——Convert BST to Greater Tree

LINTCODE——Convert BST to Greater Tree

思路：考的就是另外一种遍历方式，记前序、中序、后序遍历分别为：MLR、LMR、LRM，那么题目就是要求你用RML这种遍历方式遍历更新就好了；

class Solution {
private:
    int s = 0;
public:
    /*
     * @param root: the root of binary tree
     * @return: the new root
     */
    TreeNode * convertBST(TreeNode * root) {
        // write your code here


        if(root == NULL)
            return NULL;
       convertBST(root -> right);
       root -> val += s;
       s = root -> val;
       convertBST(root -> left);

        return root; 

    }

};