LeetCode/101.symmetric-tree.java at master · C7ABT/LeetCode · GitHub

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/*
 * @lc app=leetcode id=101 lang=java
 *
 * [101] Symmetric Tree
 */

// @lc code=start
/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public boolean isMirror(TreeNode t1, TreeNode t2) {
        if (t1 == null && t2 == null) {
            return true;
        }   else if (t1 == null || t2 == null) {
            return false;
        }
        return (t1.val == t2.val) && isMirror(t1.left, t2.right) && isMirror(t1.right, t2.left);
    }
    public boolean isSymmetric(TreeNode root) {
        return isMirror(root, root);
    }
}
// @lc code=end