3/19/2016 5:40 PMLinked list1 Array-based List v.s. Linked List Yumei Huo Department of Computer Science College of Staten Island, CUNY Spring 2009

Linked List v.s. Array-based list Array-based list Elements are stored in contiguous array positions  Support Random Access Requires an estimate of the maximum size of the list  the size of a C++ array is fixed  waste space Linked list Ensure that the list is not stored contiguously  use a linked list  a series of structures that are not necessarily adjacent in memory The pointer implementation uses only as much space as is needed for the elements currently on the list  Dynamic: a linked list can easily grow and shrink in size.  We don’t need to know how many nodes will be in the list. They are created in memory as needed. Requires space for the pointers in each cell 3/19/2016 5:40 PMLinked list2

3/19/2016 5:40 PMLinked list3 Linked List v.s. Array-based list: Access the kth element Linked List: Need to visit k nodes O(k) Array: Access the element with index k-1 directly O(1) ABCD  first Singly Linked List ABCD S[10] S[3] Array

3/19/2016 5:40 PMLinked list4 Linked List v.s. Array-based list: Search a key Linked List: Worst case: need to visit n nodes Average: need to visit n/2 nodes O(n) Array: Worst case: need to visit n nodes Average: need to visit n/2 nodes O(n)

3/19/2016 5:40 PMLinked list5 Linked List v.s. Array-based list: Insert an element to 1 st position Linked List: Visit one node O(1) Array: requires first pushing the entire array down one spot to make room Visit n node O(n)

3/19/2016 5:40 PMLinked list6 Linked List v.s. Array-based list: Delete the 1 st element Linked List: Visit one node O(1) Array: Requires shifting all the elements in the list up one Visit n node O(n)

3/19/2016 5:40 PMLinked list7 Linked List v.s. Array-based list: Insert an element to k th position Linked List: In order to find k-1 th element, k-1 nodes will be visited O(k) Array: requires first pushing the elements after k-1 th element down one spot to make room shifting n-(k-1) node Average: n/2 nodes need to be visited.

3/19/2016 5:40 PMLinked list8 Linked List v.s. Array-based list: Delete the k st element Linked List: In order to find k-1 th element, k-1 nodes will be visited O(k) Array: Requires shifting all the elements in the list up one shifting n-k node Average: n/2 nodes need to be visited.

Linked List v.s. Array-based list The Most Efficient Operations on Linked List are: Inserting at the head position O(1) Removing the head node ----O(1) If the above two operations need to be done more frequently, then linked list is the best. The Most Efficient Operations on Array-based List are: Find the kth element ----O(1) If finding the kth element needs to be done more frequently, then Array-based list is the best. 3/19/2016 5:40 PMLinked list9

3/19/2016 5:40 PMLinked list10 Thank you!