SE102 - Linked List 1

Transcript

1. Linked Lists Week 3
2. HackerRanks • Go over solution guides • Use your score as a way to gauge whether you need to study more
3. What is a Linked List?
4. What is a Linked List? Individual elements (nodes) that each hold two pieces of information:
5. What is a Linked List? Individual elements (nodes) that each hold two pieces of information: 1) data (integer, string, anything!) 2) reference to the next node
7. class LinkedListNode {
 String data;
 LinkedListNode next;
 
 LinkedListNode(String data) {
 this.data = data;
 }
 }
8. class LinkedListNode {
 String data;
 LinkedListNode next;
 
 LinkedListNode(String data) {
 this.data = data;
 }
 } LinkedListNode head = LinkedListNode head = new LinkedListNode("a");

9. class LinkedListNode {
 String data;
 LinkedListNode next;
 
 LinkedListNode(String data) {
 this.data = data;
 }
 } LinkedListNode head = LinkedListNode head = new LinkedListNode("a");
 LinkedListNode n1 = new LinkedListNode("b");
 LinkedListNode n2 = new LinkedListNode("c");
 LinkedListNode n3 = new LinkedListNode("d");
 

10. class LinkedListNode {
 String data;
 LinkedListNode next;
 
 LinkedListNode(String data) {
 this.data = data;
 }
 } LinkedListNode head = LinkedListNode head = new LinkedListNode("a");
 LinkedListNode n1 = new LinkedListNode("b");
 LinkedListNode n2 = new LinkedListNode("c");
 LinkedListNode n3 = new LinkedListNode("d");
 
 head.next = n1;
 n1.next = n2;
 n2.next = n3;
11. Why are they useful?
12. Why are they useful? Web browser’s history (previous / next page)
13. Why are they useful? Web browser’s history (previous / next page) Memory management (blocks of memories)
14. Why are they useful? Web browser’s history (previous / next page) Memory management (blocks of memories) Hash tables (resolving collisions)
15. Types of Linked Lists
16. Singly linked Types of Linked Lists
17. Singly linked Doubly linked Types of Linked Lists
18. Singly linked Doubly linked Circularly linked Types of Linked Lists
19. Singly linked Doubly linked Circularly linked Types of Linked Lists
20. Pros and Cons Always think about space / time complexity when choosing a data structure!
21. Pros and Cons Always think about space / time complexity when choosing a data structure! Good for:
 - insertion / deletion from one end 
 

22. Pros and Cons Always think about space / time complexity when choosing a data structure! Good for:
 - insertion / deletion from one end 
 
 Bad for:
 - searching
23. Pros and Cons Always think about space / time complexity when choosing a data structure! Good for:
 - insertion / deletion from one end 
 
 Bad for:
 - searching https://guides.codepath.org/compsci/Linked-Lists
24. Understand Match Pseudocode / Plan Implement Review Evaluate
25. Understand Match Pseudocode / Plan Implement Review Evaluate
26. Understand If you don’t understand the problem completely, you can’t solve it correctly
27. Understand If you don’t understand the problem completely, you can’t solve it correctly Interviewers often give vague questions to test your ability to gather requirements
28. Understand Asking clarifying questions
29. Understand Asking clarifying questions
 
 - is x input possible?

30. Understand Asking clarifying questions
 
 - is x input possible?
 - will the input always be sorted?

31. Understand Asking clarifying questions
 
 - is x input possible?
 - will the input always be sorted?
 - are there any space and time constraints?

32. Understand Asking clarifying questions
 
 - is x input possible?
 - will the input always be sorted?
 - are there any space and time constraints?
 - given x input, is the expected output y?
33. Group Exercise Work together in groups to practice Understanding the problem
34. Group Exercise Work together in groups to practice Understanding the problem - write out the method stub for the problem (what should this method return? what kind of inputs will should this method take in?)
 - list out at least 3 different input / output examples
 short input, long input, edge case
 - additional possible edge cases?
 - are any other clarifying questions needed?
35. Group Exercise Work together in groups to practice Understanding the problem - write out the method stub for the problem (what should this method return? what kind of inputs will should this method take in?)
 - list out at least 3 different input / output examples
 short input, long input, edge case
 - additional possible edge cases?
 - are any other clarifying questions needed? The goal is to gather enough information to be able to solve the problem, but you don’t need to know how you’re going to solve it yet
36. Example 1 Reverse a singly linked list
37. Example 1 Reverse a singly linked list
 
 - should our method return a new node?
 

38. Example 1 Reverse a singly linked list
 
 - should our method return a new node?
 
 void reverse(ListNode node) {
 }
39. Example 1 Reverse a singly linked list Given.. 1
 Do we return … 1 ?
 

40. Example 1 Reverse a singly linked list Given.. 1
 Do we return … 1 ?
 
 Given.. 1->2->3
 Do we return … 3->2->1 ?
 

41. Example 1 Reverse a singly linked list Given.. 1
 Do we return … 1 ?
 
 Given.. 1->2->3
 Do we return … 3->2->1 ?
 
 Given.. 1->1->1
 Do we return… 1->1->1 ?
 

42. Example 1 Reverse a singly linked list Given.. 1
 Do we return … 1 ?
 
 Given.. 1->2->3
 Do we return … 3->2->1 ?
 
 Given.. 1->1->1
 Do we return… 1->1->1 ?
 
 Can we use extra space?

43. Example 1 Reverse a singly linked list Given.. 1
 Do we return … 1 ?
 
 Given.. 1->2->3
 Do we return … 3->2->1 ?
 
 Given.. 1->1->1
 Do we return… 1->1->1 ?
 
 Can we use extra space?
 Do we have to do it in one pass?
44. Example 2 Remove duplicates from a linked list
 
 - do we want to return a new list or delete duplicates from the original?
 

45. Example 2 Remove duplicates from a linked list
 
 - do we want to return a new list or delete duplicates from the original?
 
 void removeDuplicates(ListNode node) {
 }
46. Example 2 Remove duplicates from a linked list What kind of data does the linked list hold (integers, strings)?

47. Example 2 Remove duplicates from a linked list What kind of data does the linked list hold (integers, strings)?
 Do we remove the duplicates and keep one of them? ie: 1->1->2 becomes 1->2 

48. Example 2 Remove duplicates from a linked list What kind of data does the linked list hold (integers, strings)?
 Do we remove the duplicates and keep one of them? ie: 1->1->2 becomes 1->2 
 Is the linked list always sorted already?

49. Example 2 Remove duplicates from a linked list What kind of data does the linked list hold (integers, strings)?
 Do we remove the duplicates and keep one of them? ie: 1->1->2 becomes 1->2 
 Is the linked list always sorted already?
 Can we use extra space?

50. Example 2 Remove duplicates from a linked list What kind of data does the linked list hold (integers, strings)?
 Do we remove the duplicates and keep one of them? ie: 1->1->2 becomes 1->2 
 Is the linked list always sorted already?
 Can we use extra space?
 Do we have to do it in one pass?

51. Example 2 Remove duplicates from a linked list What kind of data does the linked list hold (integers, strings)?
 Do we remove the duplicates and keep one of them? ie: 1->1->2 becomes 1->2 
 Is the linked list always sorted already?
 Can we use extra space?
 Do we have to do it in one pass?
 Given… 1, Return.. 1?
 Given… 1->1->1, Return… 1?
 Given… 1->2->3->4->4->5->5, Return… 1->2->3->4->5?
52. Group Exercise In a moment, we’re going to be assigned to break out rooms of 3-4 people
53. Group Exercise In a moment, we’re going to be assigned to break out rooms of 3-4 people Once you’re in your break out room, navigate to the course portal and go to Week 3’s Session 1 tab
54. Group Exercise In a moment, we’re going to be assigned to break out rooms of 3-4 people Once you’re in your break out room, navigate to the course portal and go to Week 2’s Session 1 tab We’ll bring everybody back to the main room in 30 minutes (with a 5 minute warning beforehand)
55. Let’s discuss the problems together!
56. Questions?