[LeetCode]101. Symmetric Tree

public boolean isSymmetric(TreeNode root) {
if(root == null){
return true;
}
return compare(root.left, root.right);
}
public boolean compare(TreeNode left, TreeNode right){
if((left == null && right != null)||(left != null && right == null)){
return false;
}
if(left == null && right == null){
return true;
}
if(left.val != right.val){
return false;
}
boolean left_ = compare(left.left, right.right);
boolean right_ = compare(left.right, right.left);
return left_ && right_;
}