private Node deleteMin(Node x){
  if (x.left == null)   return x.right;
  x.left=deleteMin(x.left);
  x.size=1 + size(x.left) + size(x.right);
  x.height=1 + Math.max(height(x.left),height(x.right));
  return balance(x);
}

private Node deleteMin ( Node x ) { if ( x . left == null ) return x . right ; x . left = deleteMin ( x . left ) ; x . size = 1 + size ( x . left ) + size ( x . right ) ; x . height = 1 + Math . max ( height ( x . left ) , height ( x . right ) ) ; return balance ( x ) ; }
removes the smallest key and associated value from the given subtree .
