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Java Solution for LeetCode algorithm problems, continually updating
package g0101_0200.s0101_symmetric_tree;
// #Easy #Top_100_Liked_Questions #Top_Interview_Questions #Depth_First_Search #Breadth_First_Search
// #Tree #Binary_Tree #Data_Structure_I_Day_11_Tree #Level_2_Day_15_Tree
// #2022_06_22_Time_0_ms_(100.00%)_Space_42.3_MB_(46.67%)
import com_github_leetcode.TreeNode;
/*
* 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;
* }
* }
*/
public class Solution {
public boolean isSymmetric(TreeNode root) {
if (root == null) {
return true;
}
return helper(root.left, root.right);
}
private boolean helper(TreeNode leftNode, TreeNode rightNode) {
if (leftNode == null || rightNode == null) {
return leftNode == null && rightNode == null;
}
if (leftNode.val != rightNode.val) {
return false;
}
return helper(leftNode.left, rightNode.right) && helper(leftNode.right, rightNode.left);
}
}