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48 lines (40 loc) · 934 Bytes
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Copy pathisSymmetric.java
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48 lines (40 loc) · 934 Bytes
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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
*/
class TreeNode {
int val;
TreeNode left;
TreeNode right;
TreeNode(int x) { val = x; }
}
public class isSymmetric{
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) || (left != null && right == null)) {
return false;
}
if (left == null && right == null) {
return true;
}
return left.val == right.val && helper(left.left, right.right) && helper(left.right, right.left);
}
public static void main(String[] args) {
}
}