0538-ConvertBSTToGreaterTree.cs

//-----------------------------------------------------------------------------
// Runtime: 104ms
// Memory Usage: 29.2 MB
// Link: https://leetcode.com/submissions/detail/342542097/
//-----------------------------------------------------------------------------

namespace LeetCode
{
    /**
     * Definition for a binary tree node.
     * public class TreeNode {
     *     public int val;
     *     public TreeNode left;
     *     public TreeNode right;
     *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
     *         this.val = val;
     *         this.left = left;
     *         this.right = right;
     *     }
     * }
     */
    public class _0538_ConvertBSTToGreaterTree
    {
        private int sum = 0;

        public TreeNode ConvertBST(TreeNode root)
        {
            if (root != null)
            {
                ConvertBST(root.right);
                sum += root.val;
                root.val = sum;
                ConvertBST(root.left);
            }

            return root;
        }
    }
}