//Univalue subtrees
//Count how many univalue subtrees are in any node within a Binary search tree
//Univalues are when the children of the node are equal to the value of the node, or when the children are both null

function countUnivalueSubtrees(root) {
  let count = 0;
  if(!root) return 0;
  is_uni(root, count);
  return count;
}
function is_uni(node, count) {
  //Base case. If we know that both node children are null, we know the node is a univalue, and can increment count and return true
  if(node.left === null && node.right === null) {
    count++;
    return true;
  }

  //set the boolean automatically to true, check is_uni for each search tree
  let is_unival = true;
  if(node.left !== null) {
    is_unival = is_uni(node.left) && is_unival && (node.left.val === node.val);
   }
  if(node.right !== null) {
    is_unival = is_uni(node.right) && is_unival && (node.right.val === node.val);
    }

  //We need to check if the is_unival is false so we don't run the next line of code where we add the count
  if(!is_unival) return false
  //If it's true, we want to increment the count, then return true to let the other nodes know
  count++;
  return true;
}