LeetCode - 101. Symmetric Tree(Tree, DFS, BFS, Recursion)*

문제

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

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

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

풀이

class Solution {
    public boolean isSymmetric(TreeNode root) {
        return isSymmetric(root.left, root.right);
    }
    public boolean isSymmetric(TreeNode l, TreeNode r){
        if(l==null&&r==null) return true;
        if(l==null||r==null) return false;
        if(l.val!=r.val) return false;
        return isSymmetric(l.left,r.right)&&isSymmetric(l.right, r.left);
    }
}

참고

https://leetcode.com/problems/symmetric-tree/discuss/433170/isMirror-DFS-(Recursion-OneTwo-Stacks)-%2B-BFS-(Queue)-Solution-in-Java