LeetCode-in-All
101. Symmetric Tree
Easy
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
type TreeNode struct {
Val int
Left *TreeNode
Right *TreeNode
}
/**
* Definition for a binary tree node.
* type TreeNode struct {
* Val int
* Left *TreeNode
* Right *TreeNode
* }
*/
func helper(left *TreeNode, right *TreeNode) bool {
if left == nil && right == nil {
return true
}
if left == nil || right == nil || left.Val != right.Val {
return false
}
leftRes := helper(left.Left, right.Right)
rightRes := helper(left.Right, right.Left)
return leftRes && rightRes
}
func isSymmetric(root *TreeNode) bool {
return helper(root.Left, root.Right)
}