text: Subtract LinkedList Helper is a recursive function , move till the last Node , and subtract the digits and create the Node and return the Node . If d1 < d2 , we borrow the number from previous digit .
code: Node subtractLinkedListHelper ( Node l1 , Node l2 ) { if ( l1 == null && l2 == null && borrow == false ) return null ; Node previous = subtractLinkedListHelper ( ( l1 != null ) ? l1 . next : null , ( l2 != null ) ? l2 . next : null ) ; int d1 = l1 . data ; int d2 = l2 . data ; int sub = 0 ;