[LeetCode] Symmetric

1: 递归

public class Solution {
    public boolean isSymmetric(TreeNode root) {
        if(root == null) return true;

        return isTwoTreeSymmetric(root.left, root.right);
    }

    public boolean isTwoTreeSymmetric(TreeNode node1, TreeNode node2) {
        if (node1 == null && node2 == null) return true;
        if (node1 == null || node2 == null) return false;

        if (node1.val != node2.val) return false;

        return isTwoTreeSymmetric(node1.left, node2.right) && isTwoTreeSymmetric(node1.right, node2.left);
    }
}

2: 非递归