This document discusses arrays in C/C++. Some key points: - Arrays allow storing multiple values of the same type in consecutive memory locations referred by a common name. Elements are accessed using an index in square brackets. - Arrays must be declared with a type, name, and size. They can be initialized with values. Multidimensional arrays represent tables with rows and columns accessed using multiple indices. - Common array operations include passing them to functions by name only, sorting and searching elements (linearly or binary), and traversing through nested for loops. Arrays provide an efficient way to organize related data.

1. ARRAYS

2. ARRAYS
• Array
• Consecutive group of memory locations
• Same name and type
• Format: arrayname[ position number ]
• First element at position 0
• n element array c:
c[ 0 ], c[ 1 ]…c[ n - 1 ]
• Array elements are like normal variables
c[ 0 ] = 3;
cout << c[ 0 ];
• Performing operations in subscript. If x = 3,
c[ 5 – 2 ] == c[ 3 ] == c[ x ]

3. ARRAYS
c[6]
-45
6
0
72
1543
-89
0
62
-3
1
6453
78
Name of array (Note that all
elements of this array have
the same name, c)
c[0]
c[1]
c[2]
c[3]
c[11]
c[10]
c[9]
c[8]
c[7]
c[5]
c[4]
Position number of the element
within array c

4. DECLARING ARRAYS
• Declaring arrays - specify:
• Name
• Type of array
• Number of elements
• Examples
int c[ 10 ];
float hi[ 3284 ];
• Declaring multiple arrays of same type
• Similar format as other variables
• Example
int b[ 100 ], x[ 27 ];

5. EXAMPLES USING ARRAYS
• Initializers
int n[ 5 ] = { 1, 2, 3, 4, 5 };
• If not enough initializers, rightmost elements become 0
• If too many initializers, a syntax error is generated
int n[ 5 ] = { 0 }
• Sets all the elements to 0
• If size omitted, the initializers determine it
int n[] = { 1, 2, 3, 4, 5 };
• 5 initializers, therefore n is a 5 element array

6. EXAMPLES USING ARRAYS
• Strings
• Arrays of characters
• All strings end with null ('0')
• Examples:
char string1[] = "hello";
char string1[] = { 'h', 'e', 'l', 'l', 'o',
'0’ };
• Subscripting is the same as for a normal array
String1[ 0 ] is 'h'
string1[ 2 ] is 'l'
• Side effect: if too much text entered, data written
beyond array

7. PASSING ARRAYS TO FUNCTIONS
• Specify the name without any brackets
• To pass array myArray declared as
int myArray[ 24 ];
to function myFunction, a function call would
resemble
myFunction( myArray, 24 );
• Array size is usually passed to function
• Arrays passed call-by-reference
• Value of name of array is address of the first element
• Function knows where the array is stored
• Modifies original memory locations
• Individual array elements passed by call-by-value
• pass subscripted name (i.e., myArray[ 3 ]) to function

8. PASSING ARRAYS TO FUNCTIONS
• Function prototype:
void modifyArray( int b[], int arraySize );
• Parameter names optional in prototype
• int b[] could be simply int []
• int arraysize could be simply int

9. SORTING ARRAYS
• Sorting data
• Important computing application
• Virtually every organization must sort some data
• Massive amounts must be sorted
• Bubble sort (sinking sort)
• Several passes through the array
• Successive pairs of elements are compared
• If increasing order (or identical), no change
• If decreasing order, elements exchanged
• Repeat these steps for every element

10. SORTING ARRAYS
• Example:
• Original: 3 4 2 6 7
• Pass 1: 3 2 4 6 7
• Pass 2: 2 3 4 6 7
• Small elements "bubble" to the top

11. SEARCHING ARRAYS: LINEAR
SEARCH AND BINARY SEARCH
• Search array for a key value
• Linear search
• Compare each element of array with key value
• Useful for small and unsorted arrays
• Binary search
• Can only be used on sorted arrays
• Compares middle element with key
• Very fast; at most n steps, where 2^n > # of elements
• 30 element array takes at most 5 steps
• 2 > 30

12. MULTIPLE-SUBSCRIPTED ARRAYS
• Multiple subscripts - tables with rows, columns
• Like matrices: specify row, then column.
• Initialize
int b[ 2 ][ 2 ] = { {1, 2}, {3, 4}};
Initializers grouped by row in braces
int b[ 2 ][ 2 ] = { { 1 }, { 3, 4 } };
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 ]
Row subscript
Array name
Column subscript
1 2
3 4
1 0
3 4

13. MULTIPLE-SUBSCRIPTED ARRAYS
• Referenced like normal
cout << b[ 0 ][ 1 ];
• Will output the value of 0
• Cannot reference with commas
cout << b( 0, 1 );
• Will try to call function b, causing a syntax
error

14. TWO DIMENSIONALARRAY
• The two-dimensional array can be defined as an
array of arrays.
• The 2D array is organized as matrices which can be
represented as the collection of rows and columns.
• It provides ease of holding the bulk of data at once
which can be passed to any number of functions
wherever required.
• The syntax to declare the 2D array is:
data_type array_name[rows][columns];

15. TWO DIMENSIONALARRAY
int main(){
int i=0,j=0;
int arr[4][3]={{1,2,3},{2,3,4},{3,4,5},{4,5,6}};
//traversing 2D array
for(i=0;i<4;i++){
for(j=0;j<3;j++){
printf("arr[%d] [%d] = %d n",i,j,arr[i][j]);
}//end of j
}//end of i
return 0;
}
arr[0][0] = 1
arr[0][1] = 2
arr[0][2] = 3
arr[1][0] = 2
arr[1][1] = 3
arr[1][2] = 4
arr[2][0] = 3
arr[2][1] = 4
arr[2][2] = 5
arr[3][0] = 4
arr[3][1] = 5
arr[3][2] = 6

16. PASSING ARRAY TO FUNCTION
1. return_type function(type arrayname[])
• Declaring blank subscript notation [] is the widely used
technique.
2. return_type function(type arrayname[SIZE])
• Optionally, we can define size in subscript notation [].
3. return_type function(type *arrayname)
• You can also use the concept of a pointer.