CS 280 Data Structures Professor John Peterson

Examples N copies?

Examples LI copies(int n, int v) { if (n <= 0) return null; return new LI(v, copies(n-1, v)) Let’s use LI to mean Link

Examples upto?

Examples LI upto(int n) { return upto1(1,n);} LI upto1(int i, int n) { if (i > n) return null; return new LI(i, upto1(i+1, n)) }

Exercises We’ll do these on the board in pairs. Sum a list of integers: int sumLI(LI l) Search a list of integers for a given value: boolean searchLI(int v, LI l) As above, except return the position: whereLI – use “-1” as the magic cookie for “not found”. int whereLI(int v, LI l); Compare two lists of integers: boolean equalsLI(LI 1, LI 2) Append two lists, destructive: LI appendLId(LI x, LI y) Append two lists, non-destuctive: LI appendLI(LI x, LI y)

Returning Two Values We’ll be creating functions that return more than one value. We could create a custom “pairing” class that is specific to the classes we need to return, but there’s a better way. How can we use a class to return a pair? How can we make this generic?

Generic Pairs We’re going to need a new Generic function class: public class Pair { public T first; public S second; public Pair(T first, S second) { this.first = first; this.second = second; }}

Quiz