題目描述:
代碼實現:
- 遞歸法,遍歷樹,判斷左右節點是否相等即可。
- 時間複雜度:O(n)
/**
* Definition for a binary tree node.
* function TreeNode(val) {
* this.val = val;
* this.left = this.right = null;
* }
*/
/**
* @param {TreeNode} root
* @return {boolean}
*/
var isSymmetric = function(root) {
if (root === null) return true
return issymmetric(root.left, root.right)
};
var issymmetric = (left, right) => {
if (left === null && right === null) {
return true
}
if (left === null || right === null) {
return false
}
return left.val === right.val && issymmetric(left.left, right.right) && issymmetric(left.right, right.left)
}