Introduction to Programming (Java) 9/11 · Introduction to Programming (Java) 2008/2009....

Introduction to Programming (Java) 9/11 1/39

Introduction to Programming (Java)9/11

Michal Krátký

Department of Computer ScienceTechnical University of Ostrava

Introduction to Programming (Java)2008/2009


Linear Data Structures

Dynamic Array

Dynamic Memory Allocation

Variables of primitive data types are stored on a stackOperation system provides a memory, heap, for a program.This memory is allocated by the new operatorWe do not delete the allocated memory (like in the case ofC++), since Garbage collector frees the unused memoryA detection: There is no pointer to an unused memory

The positive: programmer does not care about thisThe negative: overhead is higher



Dynamic Array

Dynamic Array

In the case of a dynamic array, we must resize theallocated memory if the array overflows

This reallocation has high overhead. ⇒ It is not efficient toresize the array after the insertion of each item

Therefore, we handle these variables:capacity – the size of the allocated memorysize – the number of inserted items

Issues

Arrays for various data types



Dynamic Array

DynamicArray 1/5, createArray()

public class DynamicArray{

s t a t i c i n t INDEX_SIZE = 0 ;s t a t i c i n t INDEX_FIRST_ITEM = 1 ;

s t a t i c i n t [ ] c rea teAr ray ( i n t capac i t y ){

i n t ar ray [ ] = new i n t [ capac i t y ] ;/ / the f i r s t i tem inc ludes the ar ray s ize/ / ( the number o f i tems i n the ar ray )ar ray [ INDEX_SIZE ] = 0 ;return ar ray ;

}



Dynamic Array

Dynamic Array, Implementation

INDEX_SIZE

INDEX_FIRST_ITEM

array.length-1It means

capacity=array.length-1



Dynamic Array

Dynamic Array, Implementation

1

INDEX_SIZE

0insert(0):

2 0 1insert(1):

INDEX_SIZE



Dynamic Array

DynamicArray 2/5, insert()

public s t a t i c i n t [ ] i n s e r t ( i n t [ ] array , i n t i tem ){

i n t [ ] newArray = ar ray ;

i f ( a r ray . leng th <= ar ray [ INDEX_SIZE ]+1){

/ / a r ray over f lows = > res i ze i tnewArray = res i ze ( ar ray ) ;

}newArray [ INDEX_FIRST_ITEM + newArray [ INDEX_SIZE ] ] = i tem ;newArray [ INDEX_SIZE ]++ ;

/ / p o i n t e r to the ar ray would by changed , r e t u r n the p o i n t e rreturn newArray ;

}



Dynamic Array

DynamicArray 3/5, resize() and copy()

s t a t i c i n t [ ] r es i ze ( i n t [ ] a r ray ){

i n t [ ] newArray = new i n t [ 2 ∗ ar ray . leng th ] ;copy ( array , newArray ) ;return newArray ;

}

/ / copy a l l i tem from srcAr ray to destArrays t a t i c void copy ( i n t [ ] srcArray , i n t [ ] destArray ){

for ( i n t i = 0 ; i < srcAr ray . leng th ; i ++){

destArray [ i ] = srcAr ray [ i ] ;}

}



Dynamic Array

Dynamic Array, Resize

6

INDEX_SIZE

0 1 2 3 4 5

insert(6):

insert(5):

6 0 1 2 3 4 5

newArray

After copying

7 0 1 2 3 4 5 6After insertion

INDEX_SIZE

Notice: The old small array is destroyed by Garbage Collector



Dynamic Array

DynamicArray 4/5, print()

/ / p r i n t on ly i tems of t h i s ar rays t a t i c void p r i n t ( i n t [ ] a r ray ){

for ( i n t i = 0 ; i < ar ray [ INDEX_SIZE ] ; i ++){

System . out . p r i n t ( a r ray [ INDEX_FIRST_ITEM + i ] + " , " ) ;}System . out . p r i n t ( " \ n " ) ;

}



Dynamic Array

DynamicArray 5/5, main()

public s t a t i c void main ( S t r i n g [ ] args ){

f i n a l i n t capac i t y = 1 0 ;

i n t [ ] a r ray = createAr ray ( capac i t y ) ;

for ( i n t i = 0 ; i < 5 0 ; i ++){

ar ray = i n s e r t ( array , i ) ;}p r i n t ( a r ray ) ; / / r e s u l t : 0 , 1 , . . . 4 9

}}



Dynamic Sorted Array

Sorted Array

We can sort each item that is inserted into an array

In this case, we must search the appropriate item locationin the array

Sequence or binary searching may be applied




DynamicSortedArray 1/6, createArray()

public class DynamicSortedArray{

s t a t i c i n t INDEX_SIZE = 0 ;s t a t i c i n t INDEX_FIRST_ITEM = 1 ;

s t a t i c i n t [ ] c rea teAr ray ( i n t capac i t y ){

i n t ar ray [ ] = new i n t [ capac i t y ] ;a r ray [ INDEX_SIZE ] = 0 ;return ar ray ;

}




DynamicSortedArray 2/6, insert()

public s t a t i c i n t [ ] i n s e r t ( i n t [ ] array , i n t i tem ){

i n t [ ] newArray = ar ray ;

i f ( a r ray . leng th <= ar ray [ INDEX_SIZE ]+1){

/ / a r ray i s f u l l ? res i ze t h i s ar ray . . .newArray = res i ze ( ar ray ) ;

}

/ / s o r t t h i s i tem i n t o the ar rayi nse r tAndSor t ( newArray , i tem ) ;

/ / increment the number o f i tems i n the ar raynewArray [ INDEX_SIZE ]++ ;

return newArray ;}




DynamicSortedArray 3/6, insertAndSort() 1/2

s t a t i c void i nse r tAndSor t ( i n t [ ] array , i n t i tem ){

/ / search the appropr ia te l o c a t i o ni n t index ;

i f ( a r ray [ INDEX_SIZE ] ! = 0 ){

index = ar ray [ INDEX_SIZE ] ;for ( i n t i = 0 ; i < ar ray [ INDEX_SIZE ] ; i ++){

i f ( i tem < ar ray [ INDEX_FIRST_ITEM + i ] ){

index = i ;break ;

}}

}else{

index = 0 ;}




DynamicSortedArray 4/6, insertAndSort() 2/2

/ / s h i f t a l l g rea te r i temsfor ( i n t i = ar ray [ INDEX_SIZE ] ; i > index ; i−−){

a r ray [ INDEX_FIRST_ITEM + i ] = ar ray [ INDEX_FIRST_ITEM + i − 1 ] ;}

a r ray [ INDEX_FIRST_ITEM + index ] = i tem ;}




DynamicSortedArray 5/6, resize() and print()

s t a t i c i n t [ ] r es i ze ( i n t [ ] a r ray ){

i n t [ ] newArray = new i n t [ 2 ∗ ar ray . leng th ] ;

/ / we can use t h i s method ins tead of ’ i tem by i tem ’ copyingSystem . arraycopy ( array , 0 , newArray , 0 , a r ray . leng th ) ;

return newArray ;}

s t a t i c void p r i n t ( i n t [ ] a r ray ){

for ( i n t i = 0 ; i < ar ray [ INDEX_SIZE ] ; i ++){

System . out . p r i n t ( a r ray [ INDEX_FIRST_ITEM + i ] + " , " ) ;}System . out . p r i n t ( " \ n " ) ;

}




DynamicSortedArray 6/6, main()


f i n a l i n t CAPACITY = 1 0 ;f i n a l i n t COUNT = 5 0 ;

i n t [ ] a r ray = createAr ray (CAPACITY ) ;

for ( i n t i = COUNT−1 ; i > = 0 ; i −−){

a r ray = i n s e r t ( array , i ) ;}p r i n t ( a r ray ) ; / / Resul t : 0 , 1 , . . . , 4 9

}}



Queue

Queue

Queue is a FIFO (first in, first out) data structureIt means, the first removed item is the first added item ofthe queue

Operations

Put – item insertionGet – item removingEmpty – test of the empty queue

If there is no memory for the next added item, overflowappears. On the other hand, if we want to get item from theempty queue, underflow appears.



Queue

Queue, Implementation

We need two pointersThe first pointer, head, references the queue’s first item.This item is retrieved when the Get operation is invoked.The second pointer, tail, references the queue’s last item.

head tail



Queue

Queue 1/5

public class Queue{

public s t a t i c i n t INDEX_TAIL = 0 ;public s t a t i c i n t INDEX_FIRST_ITEM = 1 ;

public s t a t i c i n t [ ] createQueue ( i n t capac i t y ){

i n t [ ] a r ray = new i n t [ capac i t y ] ;a r ray [ INDEX_TAIL ] = 0 ;return ar ray ;

}



Queue

Queue 2/5, put()

public s t a t i c boolean put ( i n t [ ] arrayQueue , i n t i tem ){

boolean r e t = fa lse ;i f ( arrayQueue [ INDEX_TAIL ] < arrayQueue . length −1){

arrayQueue [ INDEX_TAIL ]++ ;arrayQueue [ arrayQueue [ INDEX_TAIL ] ] = i tem ;r e t = true ;

}return r e t ;

}



Queue

Queue, Implementation

1

INDEX_TAIL

10put(10)

2

INDEX_TAIL

10 20put(20)

1

INDEX_TAIL

20get()

In our implementation head = 1



Queue

Queue 3/5, get()

public s t a t i c i n t get ( i n t [ ] arrayQueue ){

i n t value ;

i f ( ! empty ( arrayQueue ) ){

value = arrayQueue [ INDEX_FIRST_ITEM ] ;for ( i n t i =INDEX_FIRST_ITEM ; i <arrayQueue [ INDEX_TAIL ] ; i ++){

arrayQueue [ i ] = arrayQueue [ i + 1 ] ;}arrayQueue [ INDEX_TAIL]−−;

}else{

value = −1;}return value ;

}



Queue

Queue 4/5, empty()

public s t a t i c boolean empty ( i n t [ ] arrayQueue ){

boolean r e t = fa lse ;i f ( arrayQueue [ INDEX_TAIL ] < = INDEX_TAIL ){

r e t = true ;}return r e t ;

}



Queue

Queue 5/5, main()


f i n a l i n t CAPACITY = 1 0 ;i n t [ ] arrayQueue = createQueue (CAPACITY ) ;put ( arrayQueue , 1 0 ) ;put ( arrayQueue , 2 0 ) ;System . out . p r i n t l n ( get ( arrayQueue ) ) ; / / 10System . out . p r i n t l n ( empty ( arrayQueue ) ) ; / / f a l s e

put ( arrayQueue , 3 0 ) ;System . out . p r i n t l n ( get ( arrayQueue ) ) ; / / 20System . out . p r i n t l n ( get ( arrayQueue ) ) ; / / 30

System . out . p r i n t l n ( get ( arrayQueue ) ) ; / / −1System . out . p r i n t l n ( empty ( arrayQueue ) ) ; / / t r ue

}}



Queue

Queue

Issues

Queues for various data types

Problems

Complexity of the Get operation: O(n).We can solve this by cyclic queue

head tail headtail

Application

A buffer for data exchange



Stack

Stack

Stack is a LIFO (last-in, first out) data structure

It means, the first removed item is the last inserted item

Top: a pointer to the last inserted item

Bottom: a pointer to the last item in a stack



Stack

Stack, Operations

Push – insertion of the item in topPop – removing item in topEmpty – test of empty stackTop – return of the item in top

If a stack is empty and the Pop method is invocated, underflowappears. If it is not able to insert the next item, overflowappears.

Obviously, operations have a constant complexity.



Stack

Stack, Operations

a) Push(15); Push(6); Push(2); Push(9);

b) Push(17); Push(3);

c) Pop();



Stack

Stack 1/7, createStack()

public class Stack {s t a t i c f i n a l i n t INDEX_TOP = 0 ;s t a t i c f i n a l i n t INDEX_FIRST_ITEM = 1 ;

s t a t i c i n t [ ] c reateStack ( i n t capac i t y ){

i n t arrayStack [ ] = new i n t [ capac i t y ] ;ar rayStack [ INDEX_TOP ] = 0 ;return arrayStack ;

}



Stack

Stack 2/7, push()

s t a t i c boolean push ( i n t [ ] arrayStack , i n t value ){

boolean r e t = fa lse ;i f ( ar rayStack [ INDEX_TOP] < arrayStack . length −1){

ar rayStack [ ar rayStack [ INDEX_TOP ] + INDEX_FIRST_ITEM ] = value ;ar rayStack [ INDEX_TOP]++ ;r e t = true ;

}return r e t ;

}



Stack

Stack, Implementation

1

INDEX_TOP

0push(0)

2 0 1push(1)

INDEX_TOP

1 0pop()

INDEX_TOP



Stack

Stack 3/7, empty()

s t a t i c boolean empty ( i n t [ ] ar rayStack ){

boolean r e t = true ;i f ( ar rayStack [ INDEX_TOP] > 0 ){

r e t = fa lse ;}return r e t ;

}



Stack

Stack 4/7, top()

s t a t i c i n t top ( i n t [ ] ar rayStack ){

i n t value = −1;i f ( ! empty ( ar rayStack ) ){

value = arrayStack [ ar rayStack [ INDEX_TOP ] ] ;}return value ;

}



Stack

Stack 5/7, pop()

s t a t i c i n t pop ( i n t [ ] ar rayStack ){

i n t value = −1;i f ( ! empty ( ar rayStack ) ){

value = arrayStack [ ar rayStack [ INDEX_TOP ] ] ;ar rayStack [ INDEX_TOP]−−;

}return value ;

}



Stack

Stack 6/7, main() 1/2

public s t a t i c void main ( S t r i n g args [ ] ){

f i n a l i n t CAPACITY = 1 0 ;

i n t arrayStack [ ] = createStack (CAPACITY ) ;

for ( i n t i = 0 ; i < 1 2 ; i ++){

System . out . p r i n t ( push ( arrayStack , i ) + " , " ) ;}

System . out . p r i n t l n ( ) ;

/ / Resul t :/ / t rue , t rue , t rue , t rue , t rue , t rue , t rue , t rue , t rue ,/ / fa l se , fa l se , f a l s e



Stack

Stack 7/7, main() 2/2

for ( i n t i = 0 ; i < 1 2 ; i ++){

System . out . p r i n t ( pop ( arrayStack ) + " , " ) ;}

System . out . p r i n t l n ( ) ;/ / Resul t :/ / 8 , 7 , 6 , 5 , 4 , 3 , 2 , 1 , 0 , −1 , −1 , −1

}}



Stack

Stack

Issues

Dynamic stackStacks for various data types

Application

Replacement of recursion (QuickSort, tree searching,compilers and so on)Storage of invoked method parameters

Introduction to Programming (Java) 9/11 · Introduction to Programming (Java) 2008/2009....

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