CSE1301 Computer Programming: Lecture 33 Linked Lists

Topics Linked list List element Searching a linked list

Recall: Sorted List 01234

01234 Ann

Recall: Sorted List Ann

Recall: Sorted List Ann Dave

Recall: Sorted List Ann Dave

Recall: Sorted List Ann Dave Humphry

Recall: Sorted List Ann Dave Humphry

Recall: Sorted List Ann Dave Humphry Ben

Recall: Sorted List Ann Dave Humphry Ben

Recall: Sorted List Ann Dave Humphry Ben

Recall: Sorted List Ann Dave Humphry Ben

Recall: Sorted List Ann Dave Humphry Ben Q: Is there an alternative way to implement a sorted list? A: Linked List

01234 Ann Dave Humphry Ben First

01234 Ann Dave Humphry Ben First

01234 Ann Dave Humphry Ben First

01234 Ann Dave Humphry Ben First

01234 Ann Dave Humphry First Ben

01234 Ann Dave Humphry Ben First

01234 Ann Dave Humphry Ben First

01234 Ann Dave Humphry Ben First Amy

01234 Ann Dave Humphry Ben First Amy

01234 Ann Dave Humphry Ben First Amy

01234 Ann Dave Humphry Ben First Amy

01234 first element index of next element item invalid index (eg. -1)

Linked List Uses an array to form a sorted list Each element has a link to the next item first

List Element struct ListElementRec { int item; int next; }; typedef struct ListElementRec ListElement; 2 item next 5

What will a program have? An array of these structs ListElement list[maxListLength]; A variable to store the position of the first element of the list int first; The last element in the list must contain a non valid integer in its next field const int END = -1;

Accessing list items First element (a struct) list[first]; First item in list list[first].item; Index of next element list[first].next;

Accessing list items Next item in list int index; list[list[index].next].item; index first END

Searching in a linked list See Algorithm in Lecture Notes Example: Trace values for: index linkedList[index].item linkedList[index].next

Summary In a linked list, list elements don't have to be ordered in the array itself. A second field in the list element structure, "next", maintains the list ordering. Next lecture: adding and deleting from a linked list