text: If the current node is neither covered nor needs to be selected compulsorily
code: int ans = 1 + minDominatingSet ( root -> left , 1 , 0 ) + minDominatingSet ( root -> right , 1 , 0 ) ; if ( root -> left ) { ans = min ( ans , minDominatingSet ( root -> left , 0 , 1 ) + minDominatingSet ( root -> right , 0 , 0 ) ) ; } if ( root -> right ) { ans = min ( ans , minDominatingSet ( root -> left , 0 , 0 ) + minDominatingSet ( root -> right , 0 , 1 ) ) ; }