class Solution {
    public boolean isUnivalTree(TreeNode root) {
        return checkUniValue(root, root.val);
    }

    boolean checkUniValue(TreeNode node, int val){
        if(node==null)
            return true;

        if(node.val!=val)
            return false;

        return (checkUniValue(node.left, val) && checkUniValue(node.right, val));
    }
}