101. Symmetric Tree

https://leetcode.com/problems/symmetric-tree/

Python

DFS

class Solution:
    def isSymmetric(self, root: Optional[TreeNode]) -> bool:
        if not root:
            return False

        def check(left, right):
            if not left or not right:
                if not left and not right:
                    return True
                return False

            if left.val != right.val:
                return False

            return check(left.left, right.right) and \
                   check(left.right, right.left)

        return check(root.left, root.right)

Go

DFS

/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func isSymmetric(root *TreeNode) bool {
    if root == nil {
        return false
    }

    return check(root.Left, root.Right)
}

func check(left *TreeNode, right *TreeNode) bool {
    if left == nil && right == nil {
        return true
    }

    if left == nil || right == nil {
        return false
    }

    if left.Val != right.Val {
        return false
    }

    return check(left.Right, right.Left) && check(left.Left, right.Right)
}