1. Data Structure(s)
A way of storing and organizing data in a computer so that it can be used efficiently.
e.g.
Arrays
Linked Lists
stacks
Queues
Trees etc

2. Arrays

3. Array Consecutive group of memory locations Same name
Same type (int, char, etc.)

4. Declaring Arrays int b[ 100 ], x[ 27 ]; When declaring arrays, specify
Type of array
Name
Number of elements
type arrayName[ arraySize ];
int c[ 10 ]; // array of 10 integers
float d[ 3284 ]; // array of 3284 floats
Declaring multiple arrays of same type
Use comma separated list, like regular variables
int b[ 100 ], x[ 27 ];

5. Initializing Arrays Initializing arrays For loop Initializer list
Set each element
Initializer list
Specify each element when array declared
int n[ 5 ] = { 1, 2, 3, 4, 5 };
If not enough initializers, rightmost elements 0
If too many syntax error

6. If array size omitted, Initializer determine size
To set every element to 0
int n[ 5 ] = { 0 };
If array size omitted, Initializer determine size
int n[] = { 1, 2, 3, 4, 5 };
5 Initializer, therefore 5 element array

7. Array elements like other variables
Assignment, printing for an integer array c
c[ 0 ] = 3;
cout << c[ 0 ];
A subscript must be an integer or integer expression.
Can perform operations inside subscript
c[ 5 – 2 ] same as c[3]

8. To refer to an element N-element array c
Specify array name and position number (index/subscript)
Format: arrayname[ position number ]
First element at position 0
N-element array c
c[ 0 ], c[ 1 ] … c[ n - 1 ]
Nth element as position N-1

9. Example #include <iostream> using namespace std; void main() {
int n[ 5]={4,5, 6,10,12};
cout<<"Array elements\n";
cout<<n[0]<<endl;
cout<<n[1]<<endl;
cout<<n[2]<<endl;
cout<<n[3]<<endl;
cout<<n[4]<<endl; }

10. Example
#include <iostream> using namespace std; void main() { int n[ 10 ]={4,5, 6,10,12}; cout<<"Array elements\n"; for ( int i = 0; i < 5; i++ ) cout<<n[i]<<endl; }

11. Find the sum and average of one dimensional integer array.

12. Allow the user to input integers in an array only if the integer is even.

13. Find the smallest element of an array

14. Passing Arrays to Functions

15. Passing Arrays to Functions
Specify name without brackets
To pass array myArray to myFunction
int myArray[ 24 ];
myFunction( myArray, 24 );
Array size usually passed, but not required
Useful to iterate over all elements

16. Passing Arrays to Functions
Arrays passed-by-reference
Functions can modify original array data
Value of name of array is address of first element
Function knows where the array is stored
Can change original memory locations
Individual array elements passed-by-value
Like regular variables
square( myArray[3] );

17. Passing Arrays to Functions
Functions taking arrays
Function prototype
void modifyArray( int b[], int arraySize );
void modifyArray( int [], int );
Names optional in prototype
Both take an integer array and a single integer
No need for array size between brackets
Ignored by compiler
If declare array parameter as const
Cannot be modified (compiler error)
void doNotModify( const int [] );

18. Example (Passing Array to Functions)
void function1(int [], int); void function2(int); void main () { const int size=5; int array[]={1, 2,3 ,4,5}; cout<<"Array elements before function call:"; for (int i=0; i<5;i++) cout<<array[i]<<" "; cout<<endl;

19. function1(array, 5);
cout<<endl;
cout<<"Array elements after function call\n";
for (i=0; i<size;i++)
cout<<array[i]<<" ";
cout<<"passing array element array[2] to the function\n";
cout<<"Before:"<<array[2]<<endl;
function2(array[2]);
cout<<"After:"<<array[2]<<endl; }

20. //function definitions
void function1(int a[],int size) { cout<<"Array elements in function call\n"; for (int i=0; i<size; i++) cout<<(a[i]*=2)<<" "; } void function2( int x) { cout<<"In Function:"; cout<<x*2<<endl;

21. Searching Arrays

22. Searching Arrays: Linear Search
Search array for a key value
Linear search
Compare each element of array with key value
Start at one end, go to other
Useful for small and unsorted arrays
Inefficient
If search key not present, examines every element

23. Example (Array Search)
#include<iostream> using namespace std; void main () { const int size=10; int a[size]={ 5,6,1,8,3,7,2,10,9,4}; for(int k=0; k<size; k++) cout<<a[k]<<" "; cout<<endl; int searchKey; cout << "Enter integer search key: "; cin >> searchKey;

24. for( k=0; k<size; k++)
if (a[k]==searchKey)
cout<<"The element to be searched is found at index a["<<k<<"]";
cout<<endl; }

25. Array Sorting

26. Sorting Arrays Sorting data Bubble sort
Important computing application
Virtually every organization must sort some data
Bubble sort
Several passes through the array (assume: elements are to be sorted in increasing order)
Successive pairs of elements are compared
If increasing order (or identical), no change
If decreasing order, elements exchanged
Repeat these steps for every element

27. Sorting Arrays Example:
Go left to right, and exchange elements as necessary
One pass for each element
Original:
Pass 1: (elements exchanged)
Pass 2:
Pass 3: (no changes needed)
Pass 4:
Pass 5:

28. Sorting Arrays Swapping variables What happened? Solution
int x = 3, y = 4;
y = x;
x = y;
What happened?
Both x and y are 3!
Need a temporary variable
Solution
int x = 3, y = 4, temp = 0;
temp = x; // temp gets 3
x = y; // x gets 4
y = temp; // y gets 3

29. Example (Array Sorting)
#include<iostream> using namespace std; void main () { const int size=10; int a[size]={ 5,6,1,8,3,7,2,10,9,4}; for(int k=0; k<size; k++) cout<<a[k]<<" "; cout<<endl;

30. int temp; //sorting process for ( int pass = 0; pass < size - 1; pass++ ) for ( int j = 0; j < size - 1; j++ ) // loop to control number of comparisons per pass if ( a[ j ] > a[ j + 1 ] ) { temp = a[ j ]; a[ j ] = a[ j + 1 ]; a[ j + 1 ] = temp; } cout<<"Sorted Array\n"; for( k=0; k<size; k++) cout<<a[k]<<" "; cout<<endl;

31. Character Arrays

32. Character Arrays
2 kinds of strings
C-Strings
Objects of String class

33. Contd… Strings Arrays of characters All strings end with null ('\0')
Examples
char string1[] = "hello";
Null character implicitly added
string1 has 6 elements
char string1[] = { 'h', 'e', 'l', 'l', 'o', '\0’ };
Subscripting is the same
String1[ 0 ] is 'h'
string1[ 2 ] is 'l'

34. Contd… Input from keyboard Printing strings Puts user input in string
char string2[ 10 ];
cin >> string2;
Puts user input in string
Stops at first whitespace character
Adds null character
If too much text entered, data written beyond array
Printing strings
cout << string2 << endl;
Does not work for other array types
Characters printed until null found

35. Example (C-String Variable)
#include<iostream> using namespace std; int main () { char a[20]; cout<<"Enter String\n"; cin>>a; cout<<"you entered "<<a<<endl; return 0; }

36. Example (String Constants)
#include<iostream> using namespace std; int main () { char question[] = "Please, enter your first name: "; char greeting[] = "Hello, "; char yourname [80]; cout << question; cin >> yourname; cout << greeting << yourname << "!"<<endl; return 0; }

37. Example (Reading Embedded Blanks)
#include<iostream> using namespace std; int main () { char question[] = "Please, enter your first name: "; char greeting[] = "Hello, "; char yourname [80]; cout << question; cin.get(yourname,80); cout << greeting << yourname << "!"<<endl; return 0; }

38. Copying string
#include <iostream> using namespace std; int main() { char a1[50]="This is a string"; char a2[50]; for (int i=0;a1[i]!='\0'; i++) a2[i]=a1[i]; a2[i]='\0'; cout<<a2<<endl; return 0; }

39. Easy way!
#include <iostream> using namespace std; int main() { char a1[50]="This is a string"; char a2[50]; strcpy(a2,a1); cout<<a2<<endl; return 0; }

40. strlen, strcpy() & strcmp()
Strlen (array); tells the length of the array
Strcpy(destination, source); Copies the source values to the destination
Strcmp(str1, str2); compares two strings str1 & str2 and gives the integer value.
0 indicates the matching strings
Otherwise not same

41. String class
No need to specify array size (responsibility of memory management)
Input and output similar to C-Strings

42. Example
#include<iostream> #include<string> using namespace std; int main () { string question = "Please, enter your first name: "; string greeting ("Hello, "); string yourname; cout << question; getline(cin, yourname); cout<<greeting+yourname<<endl; return 0; }

43. 2 Dimensional Arrays

44. Multiple-Subscripted Arrays
Multiple subscripts
a[ i ][ j ]
Tables with rows and columns
Specify row, then column
“Array of arrays”
a[0] is an array of 4 elements
a[0][0] is the first element of that array
Row 0
Row 1
Row 2
Column 0
Column 1
Column 2
Column 3
a[ 0 ][ 0 ]
a[ 1 ][ 0 ]
a[ 2 ][ 0 ]
a[ 0 ][ 1 ]
a[ 1 ][ 1 ]
a[ 2 ][ 1 ]
a[ 0 ][ 2 ]
a[ 1 ][ 2 ]
a[ 2 ][ 2 ]
a[ 0 ][ 3 ]
a[ 1 ][ 3 ]
a[ 2 ][ 3 ]
Column subscript
Array name
Row subscript

45. Multiple-Subscripted Arrays
To initialize
Initializers grouped by row in braces
int b[ 2 ][ 2 ] = { { 1, 2 }, { 3, 4 } };
int b[ 2 ][ 2 ] = { { 1 }, { 3, 4 } };
1 2
3 4
Row 0
Row 1
1 0
3 4

46. Multiple-Subscripted Arrays
Referenced like normal
cout << b[ 0 ][ 1 ];
Outputs 0
Cannot reference using commas
cout << b[ 0, 1 ];
Syntax error
Function prototypes
Must specify sizes of subscripts
First subscript not necessary, as with single-scripted arrays
void printArray( int [][ 3 ] );
1 0
3 4

47. Example
//print the total of 2D array elements #include<iostream.h> int main () { int a[3][3]={1,2,3,4,5,6,7,8,9}; cout<<"Array a is:\n"; for (int i=0; i<3;i++) for (int j=0;j<3;j++) cout<<a[i][j]<<" "; cout<<endl; }

48. int total=0; for (int i=0; i<3;i++) for (int j=0;j<3;j++) total+= a[i][j]; cout<<“Total of Array elements is:”<<total<<endl return 0; }

49. Example (Passing 2D Arrays to Functions)
#include<iostream.h> void add(int a[3][3], int b[3][3]) { for (int i=0; i<3;i++) for (int j=0;j<3;j++) cout<<(a[i][j]+b[i][j])<<" "; cout<<endl; }

50. int main() { int a[][3]={1,2,3,4,5,6,7,8,9}; int b[][3]={1,2,3,4,5,6,7,8,9}; cout<<"Array a is:\n"; for (int i=0; i<3;i++) for (int j=0;j<3;j++) cout<<a[i][j]<<" "; cout<<endl; }

51. cout<<"\n\nArray b is:\n"; for (int i=0; i<3;i++) { for (int j=0;j<3;j++) cout<<a[i][j]<<" "; cout<<endl; } cout<<"\n\nSum of a & b is array:\n"; add(a,b); return 0;