/
SymmetricTree.java
46 lines (39 loc) · 1.03 KB
/
SymmetricTree.java
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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 [1,2,2,3,4,4,3] is symmetric:
// 1
// / \
// 2 2
// / \ / \
// 3 4 4 3
// But the following [1,2,2,null,3,null,3] is not:
// 1
// / \
// 2 2
// \ \
// 3 3
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class SymmetricTree {
public boolean isSymmetric(TreeNode root) {
if(root == null) {
return true;
}
return helper(root.left, root.right);
}
public boolean helper(TreeNode left, TreeNode right) {
if(left == null && right == null) {
return true;
}
if(left == null || right == null || left.val != right.val) {
return false;
}
return helper(left.right, right.left) && helper(left.left, right.right);
}
}