linked lists, stacks, and queues. oh my!...1 linked lists, stacks, and queues. oh my! announcements...
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Linked Lists, Stacks, and Queues. Oh My!
Announcements • Jotto – Due tomorrow • Apt Set 3 – Due Thursday
• Exam 1 – next Wednesday • Review – next Monday
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Assignment Submission • Include a README • Check your submissions • We will not grade it without a README • You can resubmit • but you will lose points
• APTs • all in 1 folder, no README
• Grade errors – report using form
Today • Linked Lists • Queues • Stacks
• There is a great description of Linked Lists in your textbook
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List • ArrayList
List • ArrayList
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List • ArrayList
• List – ordered collection of values
• List Interface • add(E elem) • add(int index, E elem) • contains(Obeject o) • an many more!
List • ArrayList
• List – ordered collection of values
• List Interface • add(E elem) • add(int index, E elem) • contains(Obeject o) • an many more!
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List • ArrayList
• Array – a data structure in which elements may be located by index
List • ArrayList implements List • inherits all methods from List • ArrayList implements List’s methods using an array
• ArrayList<String> array = new ArrayList<String>(); • OR • List<String> array = new ArrayList<String>();
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List • What are ArrayLists good for?
• Constant time O(1) • size • isEmpty • get • set • add*
• Linear time O(N) • everything else
* add is ~O(1)
C o m p s c i
• list.add(“C”); • list.add(“o”); • list.add(“m”); • list.add(“p”); • list.add(“s”); • list.add(“c”); • list.add(“i”);
List
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List
C o m p s c i
• How would you • add to the end, beginning, middle? • remove an element?
Linked List • LinkedList • List – ordered collection of values
• List Interface • add(E elem) • add(int index, E elem) • contains(Obeject o) • an many more!
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Linked List • LinkedList • different implementation of List from ArrayList
h e l o
myHead myTail
Linked List • LinkedList • Nodes • data • pointer to the next node
• Pointer to beginning and (sometimes) end
h e l o
myHead myTail
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Linked List • insert “l” after “e”
C o m p h e l o
myHead myTail
Linked List • insert “l” after “e” • find the location
C o m p h e l o
myHead myTail
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Linked List • insert “l” after “e” • find the location
C o m p h e l o
myHead myTail
Linked List • insert “l” after “e” • find the location • create a new node
C o m p h e l o
myHead myTail l
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Linked List • insert “l” after “e” • find the location • create a new node • update newNode to point to ‘l’
C o m p h e l o
myHead myTail l
myNext
Linked List • insert “l” after “e” • find the location • create a new node • update newNode to point to ‘l’ • update myNext to point to newNode
C o m p h e l o
myHead myTail l myNext
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Linked List • Code time
1 public void addValues(List<String> list, String file) throws FileNotFoundException{
2 Scanner s = new Scanner(new FileInputStream(file)); 3 while(s.hasNext()){ 4 list.add(s.next()); 5 } 6 } 7 8 public void removeValues(List<String> list){ 9 for (int i = 0; i < list.size(); i++){ 10 list.remove(0); 11 } 12 }
Linked List • Singly linked list
• doubly linked list
C o m p h e l o
C o m p h e l o
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Linked List • LinkedList vs. ArrayList
get add at end add in middle
LinkedList O(N) O(1) Search time + O(1)
ArrayList O(1) O(1) but O(N) worst case
Shift elements
Queue
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Queue • First In First Out (FIFO)
1 Queue<String> q = new LinkedList<String>(); 2 q.add("comp ");
3 q.add("sci "); 4 q.add("is ");
5 q.add("great!");
6 while(!q.isEmpty()) 7 System.out.print(q.remove());
comp
Queue
comp sci
• First In First Out (FIFO)
1 Queue<String> q = new LinkedList<String>(); 2 q.add("comp ");
3 q.add("sci "); 4 q.add("is ");
5 q.add("great!");
6 while(!q.isEmpty()) 7 System.out.print(q.remove());
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Queue
comp sci is
• First In First Out (FIFO)
1 Queue<String> q = new LinkedList<String>(); 2 q.add("comp ");
3 q.add("sci "); 4 q.add("is ");
5 q.add("great!");
6 while(!q.isEmpty()) 7 System.out.print(q.remove());
Queue
comp sci is great!
• First In First Out (FIFO)
1 Queue<String> q = new LinkedList<String>(); 2 q.add("comp ");
3 q.add("sci "); 4 q.add("is ");
5 q.add("great!");
6 while(!q.isEmpty()) 7 System.out.print(q.remove());
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Queue
sci is great!
• First In First Out (FIFO)
1 Queue<String> q = new LinkedList<String>(); 2 q.add("comp ");
3 q.add("sci "); 4 q.add("is ");
5 q.add("great!");
6 while(!q.isEmpty()) 7 System.out.print(q.remove());
Queue
is great!
• First In First Out (FIFO)
1 Queue<String> q = new LinkedList<String>(); 2 q.add("comp ");
3 q.add("sci "); 4 q.add("is ");
5 q.add("great!");
6 while(!q.isEmpty()) 7 System.out.print(q.remove());
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Queue
great!
• First In First Out (FIFO)
1 Queue<String> q = new LinkedList<String>(); 2 q.add("comp ");
3 q.add("sci "); 4 q.add("is ");
5 q.add("great!");
6 while(!q.isEmpty()) 7 System.out.print(q.remove());
Queue
“Comp sci is great!”
• First In First Out (FIFO)
1 Queue<String> q = new LinkedList<String>(); 2 q.add("comp ");
3 q.add("sci "); 4 q.add("is ");
5 q.add("great!");
6 while(!q.isEmpty()) 7 System.out.print(q.remove());
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Stack • Last In First Out (LIFO)
1 Stack<String> q = new Stack<String>(); 2 q.push("comp ");
3 q.push("sci "); 4 q.push("is ");
5 q.push("great!");
6 while(!q.isEmpty()) 7 System.out.print(q.pop());
comp sci is great!
Stack • Last In First Out (LIFO)
1 Stack<String> q = new Stack<String>();
2 q.push("comp ");
3 q.push("sci "); 4 q.push("is ");
5 q.push("great!"); 6 while(!q.isEmpty()) 7 System.out.print(q.pop());
comp sci is
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Stack • Last In First Out (LIFO)
1 Stack<String> q = new Stack<String>();
2 q.push("comp ");
3 q.push("sci "); 4 q.push("is ");
5 q.push("great!"); 6 while(!q.isEmpty()) 7 System.out.print(q.pop());
comp sci
Stack • Last In First Out (LIFO)
1 Stack<String> q = new Stack<String>();
2 q.push("comp ");
3 q.push("sci "); 4 q.push("is ");
5 q.push("great!"); 6 while(!q.isEmpty()) 7 System.out.print(q.pop());
comp
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Stack • Last In First Out (LIFO)
1 Stack<String> q = new Stack<String>();
2 q.push("comp ");
3 q.push("sci "); 4 q.push("is ");
5 q.push("great!"); 6 while(!q.isEmpty()) 7 System.out.print(q.pop());
“great! is comp sci”
Today • Linked Lists • Queues • Stacks