101. Symmetric Tree

Problem Statement

Given the root of a binary tree, check whether it is a mirror of itself (i.e., symmetric around its center).

Example 1:

Input: root = [1,2,2,3,4,4,3]
Output: true

Example 2:

Input: root = [1,2,2,null,3,null,3]
Output: false

Constraints:

The number of nodes in the tree is in the range [1, 1000].
-100 <= Node.val <= 100

Follow up: Could you solve it both recursively and iteratively?

Solution:

GoPython

package main

// Definition for a binary tree node.
type TreeNode struct {
	Val   int
	Left  *TreeNode
	Right *TreeNode
}

func isSymmetric(root *TreeNode) bool {
	return isMirror(root, root)
}

func isMirror(t1, t2 *TreeNode) bool {
	if t1 == nil && t2 == nil {
		return true
	}

	if t1 == nil || t2 == nil {
		return false
	}

	return (t1.Val == t2.Val) && isMirror(t1.Left, t2.Right) && isMirror(t1.Right, t2.Left)
}


from out.definitions.treenode import TreeNode


class Solution:
    def isSymmetric(self, root: TreeNode) -> bool:
        return self._is_mirror(root, root)

    def _is_mirror(self, t1: TreeNode, t2: TreeNode) -> bool:
        if not t1 and not t2:
            return True
        if not t1 or not t2:
            return False

        return ((t1.val == t2.val) and
                self._is_mirror(t1.right, t2.left) and
                self._is_mirror(t1.left, t2.right))

101. Symmetric Tree #

Problem Statement #

Solution: #

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101. Symmetric Tree

Problem Statement

Solution:

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