Arrays and Other Data Structures 4 Introduction to Arrays 4 Bounds and Subscripts 4 Integer Arrays 4 Floating Point Number Arrays 4 Lists (Linked) 4 Stacks

Introduction to Arrays 4 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. 4 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 4 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. 4 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. 4 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] row 2, col 7 might be Arizona’s high for August 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 ] ; 4 In memory, arrays are stored in row order. The first row is followed by the second row, etc. Base Address highs for state 0 12 highs for state 1 etc. Alabama Alaska first row second row STORAGE rows columns

Integer Arrays 4 We wish to store the 4-digit pager numbers for all 50 apartments in an apartment complex 4 int[] pager_numbers = new int[51]; 4 Location zero is reserved for the building manager 4 pager_number[0] = 2435;

Integer Arrays 4 Suppose that we wish to print all pager numbers from apartment#1 to apartment#50 in a nicely formatted list 4 The best way to do this would be to use the for loop

The for Statement 4 “for” is a loop statement that is controlled through a loop control variable 4 for (lcv=1; lcv<=100; lcv++) 4 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 4 int[] pagers = new int[50]; 4 int loop; 4 for (loop=1; loop<=50; loop++) 4 System.out.println(pagers[loop]);

Lists 4 Introduction to Lists 4 Contiguous Lists 4 Adding and Deleting in Contiguous Lists 4 Linked Lists 4 Pointers in Linked Lists 4 Inserting into a Linked List 4 Deleting from a Linked List

Introduction to Lists 4 An organization’s membership list may grow and shrink in size. 4 Your phone book may also grow and shrink in size as time passes 4 We need a mechanism to store dynamic lists in the memory

Linked Lists 4 Linked lists have entries connected with pointers 4 Deleting an entry can be implemented by re-arranging pointers 4 So we leave the entries where they are and just re-align the pointers

Pointers 4 Think about the pointers in your life My mailing address My Home

Pointers

4 Web links are also pointers UCLA Server Computer

Inserting into a Linked List Header Fred NE XT Bob New Entry NE XT

Inserting into a Linked List Header Fred NE XT Bob New Entry NE XT

Inserting into a Linked List Header Fred NE XT Bob NE XT

Deleting from a Linked List Header Bob NE XT Alice NE XT Fred NE XT

Deleting from a Linked List Header Bob NE XT Alice NE XT Fred NE XT

Stacks 4 Stacks 4 Stack Base and Stack Pointer 4 Push operation 4 Pop operation

Stacks 4 A stack is a useful data structure that stores values that may be needed in the near future 4 For example, you may want to return back to a website that you browsed a few moments ago 4 You may want to undo an operation that you performed in MS-Word 4 In a stack, we have a fixed size block of memory available in which we can only add and delete at one end 4 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 SB Val1 STACK WITH ONE DATA ITEM

Push Operation SP SB Val1 4 We store a data item at the location referenced by SP

Push Operation SP SB Val1 4 We store a data item at the location referenced by SP and then increment SP Val2

Push Operation 4 Stack[SP] = New Value 4 SP= SP+1; 4 The stack has a fixed maximum size of N locations. We cannot bump into other memory 4 Therefore, we must check before pushing if the stack is full 4 How?

Push Operation 4 if (SP == SB+N) 4 cout “sorry!! Stack is full”; 4 else 4{4{ 4 Stack[SP] = New_Value 4 SP= SP+1; 4}4}

Pop Operation SP SB Val1 4 We retrieve a data item from the top of stack. How can we reach top of stack value? Val2 Val3

Pop Operation SP SB Val1 4 Val3 is top of stack and it is one below the current location referenced by SP Val2 Val3

Pop Operation SP SB Val1 4 Val3 is popped out and SP is decremented to point to newly vacated location Val2

Pop Operation 4 Popped_Value = Stack[SP-1]; 4 SP= SP-1; 4 We cannot pop from an empty stack so we must check before popping 4 How?

Pop Operation 4 if (SP == SB) 4 cout “sorry!! Stack is empty”; 4 else 4{4{ 4 Popped_Value = Stack[SP-1]; 4 SP= SP-1; 4}4}

Stack Applications 4 Stacks are very useful in remembering values 4 Stacks operate similar to the way the office clerks process letters and folders 4 The current document is on top of stack and it has to be processed first 4 Stacks help programs remember the place where call to a procedure was issued