Arrays and Other Data Structures

Introduction to Arrays Bounds and Subscripts Integer Arrays Floating Point Number Arrays Lists (Linked) Stacks

Introduction to Arrays

An array is a contiguous block of the same data type. For example, you could have an array of integers (a block of integers), but not a block of integers and floats.

An integer array • int agesOfKids[n]; •Where n is the size of the block indicating the number of integers in this array

Bounds and Subscripts

Array Bounds – "Array bounds" refer to the boundaries in memory which the

array occupies. The beginning of the array (the first) element is considered the lower bound, while the end (or top) is considered to be the upper bound.

Element – An "element" is an individual entity inside the array. Because C

arrays have a lower bound of 0, array[0] refers to the first element.

Array Subscript – The expression inside the [ ... ] is known as an array subscript.

4

[0] [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11]

66 64 72 78 85 90 99 105 98 90 88 80row 2,col 7might beArizona’shigh forAugust

EXAMPLE -- To keep monthly high temperatures for all 50 states in one array.

int stateHighs [ 50 ] [12 ] ;

[ 0 ]

[ 1 ]

[ 2 ]

.

. stateHighs [2] [7]

.

[ 48 ]

[ 49 ]

5

const int NUM_STATES = 50 ;const int NUM_MONTHS = 12 ;int stateHighs [ NUM_STATES ] [ NUM_MONTHS ] ;

In memory, arrays are stored in row order. The first row

is followed by the second row, etc. Base Address

. . .

12 highs for state 0 12 highs for state 1 etc. Alabama Alaska first row second row

8000 8024 8048

STORAGErows columns

Integer Arrays

We wish to store the 4-digit pager numbers for all 50 apartments in an apartment complex

int[] pager_numbers = new int[51]; Location zero is reserved for the building

manager pager_number[0] = 2435;

Integer Arrays

Suppose that we wish to print all pager numbers from apartment#1 to apartment#50 in a nicely formatted list

The best way to do this would be to use the for loop

The for Statement

“for” is a loop statement that is controlled through a loop control variable

for (lcv=1; lcv<=100; lcv++) The above loop will start with lcv=1 and it

will run until lcv equals 100. The step size is 1 (lcv++)

Pager Numbers Printout in Java

int[] pagers = new int[50]; int loop; for (loop=1; loop<=50; loop++) System.out.println(pagers[loop]);

Lists

Introduction to Lists Contiguous Lists Adding and Deleting in Contiguous Lists Linked Lists Pointers in Linked Lists Inserting into a Linked List Deleting from a Linked List

Introduction to Lists

An organization’s membership list may grow and shrink in size.

Your phone book may also grow and shrink in size as time passes

We need a mechanism to store dynamic lists in the memory

Linked Lists

Linked lists have entries connected with pointers

Deleting an entry can be implemented by re-arranging pointers

So we leave the entries where they are and just re-align the pointers

Pointers

Think about the pointers in your life

My mailing address

My Home

Pointers

Pointers

Web links are also pointers

http://www.ucla.eduUCLA Server

Computer

Inserting into a Linked List

Header

Fred423-3158

NEXT

Bob242-7111

New Entry

NEXT

Inserting into a Linked List

Header

Fred423-3158

NEXT

Bob242-7111

New Entry

NEXT

Inserting into a Linked List

Header Fred423-3158

NEXT

Bob242-7111

NEXT

Deleting from a Linked List

HeaderBob

423-3178

NEXT

Alice242-7111

NEXT

Fred423-3158

NEXT

Deleting from a Linked List

Header

Bob423-3178

NEXT

Alice242-7111

NEXT

Fred423-3158

NEXT

Stacks

Stacks Stack Base and Stack Pointer Push operation Pop operation

Stacks

A stack is a useful data structure that stores values that may be needed in the near future

For example, you may want to return back to a website that you browsed a few moments ago

You may want to undo an operation that you performed in MS-Word

In a stack, we have a fixed size block of memory available in which we can only add and delete at one end

We keep track of both ends of stack with pointers

Stack Operation

Designated Block for

Stack

Other Memory

Stack Operation

SP

SB

EMPTY STACK

Stack Operation

SP

SBVal1

STACK WITH ONE DATA ITEM

Push Operation

SP

SBVal1

We store a data item at the location referenced by SP

Push Operation

SP

SBVal1

We store a data item at the location referenced by SP and then increment SP

Val2

Push Operation

Stack[SP] = New Value SP= SP+1; The stack has a fixed maximum size of N

locations. We cannot bump into other memory

Therefore, we must check before pushing if the stack is full

How?

Push Operation

if (SP == SB+N) cout “sorry!! Stack is full”; else { Stack[SP] = New_Value SP= SP+1; }

Pop Operation

SP

SBVal1

We retrieve a data item from the top of stack. How can we reach top of stack value?

Val2

Val3

Pop Operation

SP

SBVal1

Val3 is top of stack and it is one below the current location referenced by SP

Val2

Val3

Pop Operation

SP

SBVal1

Val3 is popped out and SP is decremented to point to newly vacated location

Val2

Pop Operation

Popped_Value = Stack[SP-1]; SP= SP-1; We cannot pop from an empty stack so we

must check before popping How?

Pop Operation

if (SP == SB) cout “sorry!! Stack is empty”; else { Popped_Value = Stack[SP-1]; SP= SP-1; }

Stack Applications

Stacks are very useful in remembering values

Stacks operate similar to the way the office clerks process letters and folders

The current document is on top of stack and it has to be processed first

Stacks help programs remember the place where call to a procedure was issued