Arrays and Other Data Structures

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# Arrays and Other Data Structures - PowerPoint PPT Presentation

Arrays and Other Data Structures. Introduction to Arrays Bounds and Subscripts Integer Arrays Floating Point Number Arrays Lists (Linked) Stacks. Introduction to Arrays.

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Presentation Transcript
Arrays and Other Data Structures
• Introduction to Arrays
• Bounds and Subscripts
• Integer Arrays
• Floating Point Number Arrays
• 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.
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 ]

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

66 64 72 78 85 90 99 105 98 90 88 80

row 2,

col 7

might be

Arizona’s

high for

August

rows columns

STORAGE

8000

8024

8048

12 highs for state 0 12 highs for state 1 etc.

first row second row

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.

. . .

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
• 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 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

My Home

Pointers
• Web links are also pointers

UCLA Server Computer

http://www.ucla.edu

NEXT

Bob

242-7111

NEXT

Fred

423-3158

New Entry

NEXT

Bob

242-7111

NEXT

Fred

423-3158

New Entry

NEXT

NEXT

Bob

242-7111

Fred

423-3158

NEXT

NEXT

NEXT

Alice

242-7111

Bob

423-3178

Fred

423-3158

NEXT

Bob

423-3178

NEXT

NEXT

Alice

242-7111

Fred

423-3158

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

Other Memory

Designated Block for Stack

Stack Operation

EMPTY STACK

SP

SB

Stack Operation

STACK WITH ONE DATA ITEM

SP

SB

Val1

Push Operation
• We store a data item at the location referenced by SP

SP

SB

Val1

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

SP

Val2

SB

Val1

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

SP

Val3

Val2

SB

Val1

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

SP

Val3

Val2

SB

Val1

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

SP

Val2

SB

Val1

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