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 != null ) { ans = Math . Min ( ans , minDominatingSet ( root . left , 0 , 1 ) + minDominatingSet ( root . right , 0 , 0 ) ) ; } if ( root . right != null ) { ans = Math . Min ( ans , minDominatingSet ( root . left , 0 , 0 ) + minDominatingSet ( root . right , 0 , 1 ) ) ; }