LeetCode 101 - Symmetric Tree - 题解/Solution

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

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/**
* Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).
* For example, this binary tree is symmetric:
*
* 1
* / \
* 2 2
* / \ / \
* 3 4 4 3
* But the following is not:
* 1
* / \
* 2 2
* \ \
* 3 3
*
* @author dongyuxi
*
*/
public class Solution {
public boolean isSymmetric(TreeNode root) {
if (null == root) {
return true;
}

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

private boolean recursiveIsSymmetric(TreeNode left, TreeNode right) {
if (null == left && null == right) {
return true;
}
if (null == left || null == right) {
return false;
}
boolean leftLeftRightRight = recursiveIsSymmetric(left.left, right.right);
boolean leftRightRightLeft = recursiveIsSymmetric(left.right, right.left);
if (leftLeftRightRight && leftRightRightLeft && left.val == right.val) {
return true;
}

return false;
}
}

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