BinaryTree_Leetcode_226. Invert Binary Tree [swift]

https://leetcode.com/problems/invert-binary-tree/description/?envType=study-plan-v2&envId=top-100-liked

 

 

문제접근

간단하게 child의 위치를 서로 바꾸면 되는 문제

정답코드

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     public var val: Int
 *     public var left: TreeNode?
 *     public var right: TreeNode?
 *     public init() { self.val = 0; self.left = nil; self.right = nil; }
 *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
 *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
 *         self.val = val
 *         self.left = left
 *         self.right = right
 *     }
 * }
 */
class Solution {
    func invertTree(_ root: TreeNode?) -> TreeNode? {
        guard var _root = root else { return nil }

        invertInner(target: &_root)

        return _root
    }

    func invertInner(target node: inout TreeNode) {
        var temp = node.left
        node.left = node.right
        node.right = temp

        if var lhs = node.left {
            invertInner(target: &lhs)
        }

        if var rhs = node.right {
            invertInner(target: &rhs)
        }
    }
}