leetcode 101対称二叉木

public boolean isSymmetric(TreeNode root) {
     
        if (root == null) return true;

        return check(root.left,root.right);
    }
    boolean check(TreeNode left,TreeNode right){
     
        if (left == null && right == null) return true;
        if (left == null || right == null) return false;
        if (left.val != right.val) return false;
        return check(left.left, right.right) && check(left.right, right.left);
    }