[Swift] LeetCode - 1038. Binary Search Tree to Greater Sum Tree

문제: https://leetcode.com/problems/binary-search-tree-to-greater-sum-tree/

Binary Search Tree to Greater Sum Tree - LeetCode

 

 

오른쪽 -> 가운데 -> 왼쪽 순서로 돌면 됩니다!

class Solution {
    var value = 0
    
    func bstToGst(_ root: TreeNode?) -> TreeNode? {
        if root != nil {
            bstToGst(root!.right)
            value += root!.val
            root!.val = value
            bstToGst(root!.left)
        }
        
        return root
    }
}