Winter 2016 COMP-250: Introduction to Computer...

Winter 2016COMP-250: Introduction

to Computer ScienceLecture 6, January 28, 2016

Java Generics

element next

|_,•|

Java Generics

Java Generics

(Doubly) Linked List

(Doubly) Linked List Node

element next prev

|9,•,•|

|•,•,⊠| |•,•,•| |•,•,•| |•,⊠,•|

head tail size

|•,•,4|

|•,•,⊠| |•,•,•| |•,•,•| |•,⊠,•|

head tail size

|•,•,4|

|•,•,⊠| |•,•,•| |•,•,•| |•,⊠,•|

head tail size

|•,•,4|

|•,•,⊠| |•,•,•| |•,•,•| |•,⊠,•|

head tail size

|•,•,4|

|•,•,⊠| |•,•,•| |•,•,•| |•,⊠,•|

head tail size

|•,•,4|

|•,•,⊠| |•,•,•| |•,•,•| |•,⊠,•|

head tail size

|•,•,4|

node

|•|

|•,•,⊠| |•,•,•| |•,•,•| |•,⊠,•|

head tail size

|•,•,4|

node

|•|

|•,•,⊠| |•,•,•| |•,•,•| |•,⊠,•|

head tail size

|•,•,4|

node

|•|

|•,•,⊠| |•,•,•| |•,•,•| |•,⊠,•|

head tail size

|•,•,4|

node

|•|

|•,•,⊠| |•,•,•| |•,•,•| |•,⊠,•|

head tail size

|•,•,4|

node

|•|

|•,•,⊠| |•,•,•| |•,•,•| |•,⊠,•|

head tail size

|•,•,4|

node

|•|3

|•,•,⊠| |•,•,•| |•,•,•| |•,⊠,•|

head tail size

|•,•,4|

node

|•|3

|•,•,⊠| |•,•,•| |•,•,•| |•,⊠,•|

head tail size

|•,•,4|

node

|•|3

⊠

|•,•,⊠| |•,•,•| |•,•,•| |•,⊠,•|

head tail size

|•,•,4|

node

|•|3

⊠

|•,•,⊠| |•,•,•| |•,•,•| |•,⊠,•|

head tail size

|•,•,4|

node

|•|3

⊠ ⊠

|•,•,⊠| |•,•,•| |•,•,•| |•,⊠,•|

head tail size

|•,•,4|

node

|•|

|•,•,⊠| |•,•,•| |•,•,•| |•,⊠,•|

head tail size

|•,•,4|

node

|•|

|•,•,⊠| |•,•,•| |•,•,•| |•,⊠,•|

head tail size

|•,•,4|

node

|•|

|⊠,•,⊠| |•,•,•| |•,•,•| |⊠,⊠,•|

dummy dummy . Head Tail size

|•,•,2|

|⊠,•,⊠| |•,•,•| |•,•,•| |⊠,⊠,•|

head tail size

|•,•,2|

node

|•|

|⊠,•,⊠| |•,•,•| |•,•,•| |⊠,⊠,•|

head tail size

|•,•,2|

node

|•|

|⊠,•,⊠| |•,•,•| |•,•,•| |⊠,⊠,•|

head tail size

|•,•,2|

node

|•|

|⊠,•,⊠| |•,•,•| |•,•,•| |⊠,⊠,•|

head tail size

|•,•,2|

node

|•|

|⊠,•,⊠| |•,•,•| |•,•,•| |⊠,⊠,•|

head tail size

|•,•,2|

node

|•|

|⊠,•,⊠| |•,•,•| |•,•,•| |⊠,⊠,•|

head tail size

|•,•,2|

node

|•|1

|⊠,•,⊠| |•,•,•| |•,•,•| |⊠,⊠,•|

head tail size

|•,•,2|

node

|•|1

|⊠,•,⊠| |•,•,•| |•,•,•| |⊠,⊠,•|

head tail size

|•,•,2|

node

|•|1

⊠

|⊠,•,⊠| |•,•,•| |•,•,•| |⊠,⊠,•|

head tail size

|•,•,2|

node

|•|1

⊠

|⊠,•,⊠| |•,•,•| |•,•,•| |⊠,⊠,•|

head tail size

|•,•,2|

node

|•|1

⊠ ⊠

Array vs Linked List

Linked Lists as ADT(Abstract Data Type)

Linked List operations

|⊠,•,⊠| |•,•,•| |•,•,•| |⊠,⊠,•|

dummy dummy . Head Tail size

|•,•,2|

Java LinkedList

• implemented as doubly linked list(with dummies)

• Node class is private

Java LinkedList

|⊠,•,⊠| |•,•,•| |•,•,•| |⊠,⊠,•|

|•,•,2|

Java LinkedList

}expensive

|⊠,•,⊠| |•,•,•| |•,•,•| |⊠,⊠,•|

|•,•,2|

Java LinkedList

Time(n) is 𝜴(n2)

|⊠,•,⊠| |•,•,•| |•,•,•| |⊠,⊠,•|

|•,•,2|

|•,•,•,•|

array size cap.

|•,4,4|

Java ArrayList

• implementation using arrays of growing sizes

• cannot access using a[i] notation

|•,•,•,•|

array size cap.

|•,4,4|

Java ArrayList

• implementation using arrays of growing sizes

• cannot access using a[i] notationelement

|•|

|•,•,•,•|

array size cap.

|•,4,4|

Java ArrayList

• when new space is needed - doubles the array size.

|•,•,•,•,•,•,•,•|

element

|•|

|•,•,•,•|

array size cap.

|•,4,4|

Java ArrayList

• smaller array is copied into bigger array.

|•,•,•,•,⊠,⊠,⊠,⊠|

element

|•|

array size cap.

|•,4,8|

Java ArrayList

• new element added to new array

|•,•,•,•,⊠,⊠,⊠,⊠|

element

|•|

|•,•,•,•,•,⊠,⊠,⊠|

array size cap.

|•,4,8|

Java ArrayList

• implementation using arrays of growing sizes

• cannot access using a[i] notation

Cost ?

|•,•,•,•|

array size cap.

|•,4,4| |•,•,•,•,⊠,⊠,⊠,⊠|

Java ArrayList

• implementation using arrays of growing sizes

• cannot access using a[i] notation

|•,•,•,•|

array size cap.

|•,4,4| |•,•,•,•,⊠,⊠,⊠,⊠|

Java ArrayList

• implementation using arrays of growing sizes

• cannot access using a[i] notationExtra cost of 2k+1 new steps only if 2k stepsalready spent before!

|•,•,•,•|

array size cap.

|•,4,4| |•,•,•,•,⊠,⊠,⊠,⊠|

Java ArrayList

• implementation using arrays of growing sizes

• cannot access using a[i] notationExtra cost of 2k+1 new steps only if 2k stepsalready spent before!

Cost is amortized constant time!

|•,•,•,•,⊠,⊠,⊠,⊠|

Java ArrayList

|•,•,•,•| |•,•| |•|20

21

22

23

|•,•,•,•,⊠,⊠,⊠,⊠|

Java ArrayList

To build an arrayof 2k elements

you need 2k+1-1 steps!

|•,•,•,•| |•,•| |•|20

21

22

23

|•,•,•,•,⊠,⊠,⊠,⊠|

Java ArrayList

To build an arrayof 2k elements

you need 2k+1-1 steps!

Cost is amortized constant time!

|•,•,•,•| |•,•| |•|20

21

22

23

|•,•,•,•|

array size cap.

|•,4,4|

Java ArrayList

• implementation using arrays of growing sizes

• cannot access using a[i] notationelement

|•|

|•,•,•,•|

array size cap.

|•,4,4|

Java ArrayList

• implementation using arrays of growing sizes

• cannot access using a[i] notationelement

|•|

|•,•,•,•|

array size cap.

|•,4,4|

Java ArrayList

• implementation using arrays of growing sizes

• cannot access using a[i] notationelement

|•|

Cost is constant!

|•,•,•,•|

array size cap.

|•,4,4|

Java ArrayList

• implementation using arrays of growing sizes

• cannot access using a[i] notationget(2)

|•|

|•,•,•,•|

array size cap.

|•,4,4|

Java ArrayList

• implementation using arrays of growing sizes

• cannot access using a[i] notationget(2)

|•|

Cost is constant!

|•,•,•,•|

array size cap.

|•,4,4|

Java ArrayList

• implementation using arrays of growing sizes

• cannot access using a[i] notationget(2)

|•|

Cost is constant!

|•,•,•,•|

array size cap.

|•,4,4|

Java ArrayList

• implementation using arrays of growing sizes

• cannot access using a[i] notationget(2)

|•|

Cost is constant!

|•,•,•,•|

array size cap.

|•,4,4|

Java ArrayList

• implementation using arrays of growing sizes

• cannot access using a[i] notationget(2)

|•|

Cost is constant!

|•,•,•,•,•,⊠,⊠,⊠|

array size cap.

|•,4,8|

Java ArrayList

• implementation using arrays of growing sizes

• cannot access using a[i] notation

|•,•,•,•,•,⊠,⊠,⊠|

array size cap.

|•,4,8|

Java ArrayList

• implementation using arrays of growing sizes

• cannot access using a[i] notationelement

|•|

|•,•,•,•,•,⊠,⊠,⊠|

array size cap.

|•,4,8|

Java ArrayList

• implementation using arrays of growing sizes

• cannot access using a[i] notationelement

|•|

⤻

|•,•,•,•,•,⊠,⊠,⊠|

array size cap.

|•,4,8|

Java ArrayList

• implementation using arrays of growing sizes

• cannot access using a[i] notationelement

|•|

⤻⤻

|•,•,•,•,•,⊠,⊠,⊠|

array size cap.

|•,4,8|

Java ArrayList

• implementation using arrays of growing sizes

• cannot access using a[i] notationelement

|•|

⤻⤻⤻

|•,•,•,•,•,⊠,⊠,⊠|

array size cap.

|•,4,8|

Java ArrayList

• implementation using arrays of growing sizes

• cannot access using a[i] notationelement

|•|

⤻⤻⤻⤻

|•,•,•,•,•,•,⊠,⊠|

array size cap.

|•,4,8|

Java ArrayList

• implementation using arrays of growing sizes

• cannot access using a[i] notationelement

|•|

|•,•,•,•,•,•,⊠,⊠|

array size cap.

|•,4,8|

Java ArrayList

• implementation using arrays of growing sizes

• cannot access using a[i] notationelement

|•|

|•,•,•,•,•,•,⊠,⊠|

array size cap.

|•,4,8|

Java ArrayList

• implementation using arrays of growing sizes

• cannot access using a[i] notationelement

|•| 5

|•,•,•,•,•,•,⊠,⊠|

array size cap.

|•,4,8|

Java ArrayList

• implementation using arrays of growing sizes

• cannot access using a[i] notationelement

|•| Cost is linear!5

|•,•,•,•,•,•,⊠,⊠|

array size cap.

|•,4,8|

Java ArrayList

• implementation using arrays of growing sizes

• cannot access using a[i] notationelement

|•| Cost is linear!

Same for Remove!5

|•,•,•,•,•,•,⊠,⊠|

array size cap.

|•,4,8|

Java ArrayList

• implementation using arrays of growing sizes

• cannot access using a[i] notationelement

|•| Cost is linear!

Same for Remove!5

LinkedList vs ArrayList

Winter 2016COMP-250: Introduction

to Computer ScienceLecture 6, January 28, 2016