Understanding Arrays and Strings in Programming

Chapter 2 Array and String

Array Array Definition of Array Definition of Array : An array is a sequence or collection of the related data items that share a common name. Purpose Purpose : To store multiple values in a single variable but of same data type. Syntax Syntax : datatype arrayname[dim1][dim2] .[dimn]; where dimension indicates number of slots. e.g. int x[5]; => This indicates one dimensional array with 5 slots. 1 2 3 4 5 x

Memory Requirement Memory Requirement Total no of bytes required for any array can be calculated as follows, bytes = size of given data type * dim1*dim2* .*dimn. e.g. int x[5] => bytes = 2*5=10 int y[5][3] => bytes = 2*5*3=30

There are mainly two types of the array: There are mainly two types of the array: One Dimentional array Two Dimentional array One One Dimentional Array: Dimentional Array: A list of items can be given one variable name using only one dimension and such a variable is called a one dimensional array. Syntax: Syntax: datatype array datatype array- -name[size]; name[size]; Ex: Ex: int a[5]; int a[5];

To access particular slot To access particular slot syntax: syntax: arrayname[logical slotno] arrayname[logical slotno] e.g. a[0] e.g. a[0]- - content of 0 content of 0th th slot(logical) slot(logical)

If & is placed before the array name with slot no then it indicates the address of corresponding slot. Initialization of one Initialization of one dimentional arrays: dimentional arrays: After an array is declared, its element must be initialized. Otherwise, they will contain garbage . An array can be initialized at either of the following stages: 1. 1.At compile time At compile time 2. 2.At run time At run time 1. Compile time initialization: 1. Compile time initialization: Syntax: Syntax: Type array Type array- -name[size] = {list of values}; name[size] = {list of values}; The value in the list are separed by commas.

Ex: Ex: int a[3] = {0,0,0} ; int a[3] = {0,0,0} ; int a[3] = {10, 20, 30, 40} ; int a[3] = {10, 20, 30, 40} ; will not work. It is illegal in C. counter array contain four element with initial value 1. Ex: Ex: int counter[] = {1,1,1,1} int counter[] = {1,1,1,1}

2. Run time initialization : 2. Run time initialization : An array can be explicitly initialized at run time. This approach is usually applied for initializing large arrays. Ex: Ex: for(i=0; i<100 ; i++) for(i=0; i<100 ; i++) { { if (i < 50 ) if (i < 50 ) sum[i] = 0.0; sum[i] = 0.0; else else sum[i] = 1.0; sum[i] = 1.0; } }

Ex: Ex: int x[3]; int x[3]; Will initialize array elements with the values entered through the keyboard. scanf ( %d%d%d , &x[0], &x[1], &x[2] ) ; scanf ( %d%d%d , &x[0], &x[1], &x[2] ) ;

Example 1 : Accept n nos. in an array and display the sum and average of these n nos. #include<stdio.h> #include<conio.h> void main() { int i,arr[20],n; float sum=0; printf("Enter the value for n (max 20): "); scanf("%d",&n); printf("Enter %d numbers : ",n); for(i=0;i<n;i++) { scanf("%d",&arr[i]); sum += arr[i]; } printf("The sum of the numbers is : %d\n",sum); printf("The average of the numbers is : %.3f\n",sum/n); getch(); }//main Output: Output: Enter the value for n (max 20): 6 Enter 6 numbers : 25 67 89 12 10 45 The sum of the numbers is : 248 The average of the numbers is : 41.3

Example 2 : Accept n elements in an array and sort the array in ascending order. #include<stdio.h> #include<conio.h> void main() { int i,arr[20],n,j,temp; printf("Enter the value for n (max 20): "); scanf("%d",&n); printf("Enter %d numbers : ",n); for(i=0;i<n;i++) scanf("%d",&arr[i]); for(i=0;i<n-1;i++) for(j=i+1;j<n;j++) if(arr[i] > arr[j]) { temp=arr[i]; arr[i]=arr[j]; arr[j]=temp; } printf("\nThe elements in ascending order are :\n"); for(i=0;i<n;i++) printf("%d\t",arr[i]); Output: Output: Enter the value for n (max 20): 6 Enter 6 numbers : 25 67 89 12 10 45 The elements in ascending order are : 10 12 25 45 67 89

Example 3 : Accept n elements in an array and find the sum of all odd numbers and even numbers. #include<stdio.h> #include<conio.h> void main() { int i,arr[20],n,sum1=0,sum2=0; printf("Enter the value for n (max 20): "); scanf("%d",&n); printf("Enter %d numbers : ",n); for(i=0;i<n;i++) scanf("%d",&arr[i]); for(i=0;i<n;i++) { if(arr[i]%2 == 0) sum1+=arr[i]; else sum2+=arr[i]; }//for printf("The sum of even numbers is %d\n",sum1); printf("The sum of odd numbers is %d\n",sum2); getch(); }//main Output: Output: Enter the value for n (max 20): 10 Enter 10 numbers : 34 11 10 5 7 32 12 66 99 3 The sum of even numbers is 154 The sum of odd numbers is 125

TWO TWO DIMENTIONAL ARRAY: DIMENTIONAL ARRAY: If you want to store data into table or matrix form at that time you can use the two dimensional array. Declaration of two Declaration of two dimentional dimentional array: array: Syntax : Syntax : data_type data_type array array- -name[dim1][dim2]; name[dim1][dim2]; Where dim1 indicates total rows and dim2 indicates total columns. Where dim1 indicates total rows and dim2 indicates total columns. Ex: Ex: ITEM 1 SALES MAN 1 310 SALES MAN 2 210 SALES MAN 3 405 SALES MAN 4 260 ITEM2 275 190 235 300 ITEM 3 365 325 240 380

Memory representation of the two Memory representation of the two dimentional column 0 column 1 column 0 column 1 [0][0] [0][0] Row 0 Row 0 [1][0] [1][0] Row 1 Row 1 [2][0] [2][0] Row Row 2 2 [3][0] [3][0] Row 3 Row 3 310 dimentional array for v[4][3] . array for v[4][3] . column2 column2 [0][1] [0][1] 275 [0][2] [0][2] 365 310 [1][1] [1][1] [1][2] [1][2] 10 190 325 [2][1] [2][1] 235 [2][2 [2][2] ] 240 405 [3][1] [3][1] 275 [3][2] [3][2] 365

Initializing two dimentional array: Initializing two dimentional array: Ex: int table[2][3] = {0,0,0,1,1,1}; Ex: int table[2][3] = {0,0,0,1,1,1}; int table[2][3] = { } ; {0,0,0}, {1,1,1}

Initializing two dimentional array: Initializing two dimentional array: When the array is completely initialized with all values, we need not specify the size of the first dimension. That is, the statement is permitted. int table[][3] = { }; {0,0,0} , {1,1,1)

If the value is missing in an initializes, they are automatically set to zero. Ex: int table[2][3] ={ Ex: int table[2][3] ={ } ; } ; int m[3][5] = { 0, 0 }; int m[3][5] = { 0, 0 }; or or int m[3][5] = { {0} , { 0} }; int m[3][5] = { {0} , { 0} }; {1,1} , {1,1} , {2} {2}

Example 1 : Write a program for addition and subtraction of two matrices. #include<stdio.h> #include<conio.h> void main() { int a[10][10],b[10][10],c[10][10],i,j,r,c; printf( \n Enter no of rows and columns ); scanf( %d%d ,&r,&c); printf("Enter %d elements of first matrix\n ,r*c); for(i=0;i<r;i++) for(j=0;j<c;j++) scanf("%d",&a[i][j]); printf("Enter %d elements of second matrix \n ,r*c);

for(i=0;i<r;i++) for(j=0;j<c;j++) scanf("%d",&b[i][j]); for(i=0;i<r;i++) for(j=0;j<c;j++) c[i][j] = a[i][j]+b[i][j]; printf("The addition of the two matrices is : \n\n"); for(i=0;i<r;i++) { for(j=0;j<c;j++) printf("%d\t",c[i][j]); printf("\n"); }

for(i=0;i<r;i++) for(j=0;j<c;j++) c[i][j] = a[i][j]-b[i][j]; printf("The subtraction of the two matrices is : \n\n"); for(i=0;i<r;i++) { for(j=0;j<c;j++) printf("%d\t",c[i][j]); printf("\n"); } getch(); }

Enter no of rows and columns 3 3 Enter 9 elements of first matrix 23 4 67 8 6 21 19 10 5 Enter 9 elements of second matrix 3 45 21 39 10 16 14 12 11 The addition of the two matrices is : 26 49 88 47 16 37 33 22 16 The subtraction of the two matrices is : 20 -41 46 -31 -4 5 5 -2 -6

Example 2 :Write a program to display the transpose of entered matrix #include<stdio.h> #include<conio.h> void main() { int a[5][5],i,j,r,c,b[5][5]; clrscr(); printf( \n Enter no of rows and columns ); scanf( %d%d ,&r,&c); printf("Enter %d elements of matrix \n r*c); for(i=0;i<r;i++) for(j=0;j<c;j++) scanf("%d",&a[i][j]); for(i=0;i<r;i++) for(j=0;j<c;j++) b[j][i]=a[i][j]);

printf("The transpose of the matrix is : \n\n"); for(i=0;i<c;i++) { for(j=0;j<r;j++) printf("%d\t ,b[i][j]); printf("\n"); } getch(); } Output: Output: Enter no of rows and columns 3 2 Enter 6 elements of matrix 12 67 90 11 34 77 The transpose of the matrix is : 12 90 34 67 11 77

String String What is a String : What is a String : String is a group of characters. String is a group of characters. Any group of character defined between double Any group of character defined between double quotation mark is a constant string. quotation mark is a constant string. Ex: printf( Hello How are you ); output : Hello How are you If you want to include double quotes with string than also it is possible. Ex: printf( \ Hello How are you \ ); output : Hello How are you

Declaring and Initialising String Variable : Declaring and Initialising String Variable : A String Variable is always declared as an array : Syntax : char string_name[size]; where size determines the number of character in the string. Size should be maximum number of the character + 1. Ex: char city[10]; char name[30];

Initialization of string variable : Initialization of string variable : char array may be initialized when they are declared. You can initialized char array with two form: char city[9] = New York ; char city[9] = { N , e , w , , Y , o , r , k , \0 };

C also permit us to initialize character array without specifying the number of elements. Ex: Ex: char string[] = { G , O , O , D , \0 }; It defines the string as five elements array.

Reading String : Reading String : Ex: Ex: char address[15]; scanf( %s ,address); (& sign is not included before address) The problem with the scanf() function is that it terminates its input on the first white space it finds. Ex: Ex: If input string is New York then in address array stores only New . After New, string will be terminated. For this reason to read the string gets() function is used which reads white spaces also. Syntax: Syntax: gets(arrayname); Ex. gets(address);

Writing string to screen : Writing string to screen : We have used printf() function with %s format to print the string to the screen. Ex: Ex: printf( %s ,name); We can use puts() function to display the string. syntax : e.g. syntax : puts(stringname); e.g. puts(name);

Features of the %s format specification : Features of the %s format specification : (1) The integer value on the right side of the decimal point specifies the number of character to be printed. Ex: %10.4s specifies 4 character printed . (2) When the number of character to be printed is specified by zero, nothing is printed. Ex: %10.0s (3) The minus sign in the specification causes the string to be printed left side. Ex: %-10.4s 4 character printed left side.

Another nice features for printing output is: Another nice features for printing output is: printf( %*.*s\n ,w,d,string); prints the first d characters of the string in the field width of w. Write the program for writing string using %s format : void main() { char country[15] = United Kingdom printf( %15s \n ,country); printf( %5s \n ,country); printf( %15.6s \n ,country); printf( %-15.6s \n ,country); printf( %15.0s \n ,country); printf( %0.3s \n ,country); } Output : Output : United Kingdom United Kingdom United United United United United United Uni Uni

The C library provides a function which converts string of digits into their integer value. Ex: number = 1988 ; year = atoi(number); String Handling function : String Handling function : There are mainly four types of string handling function: 1. strcat() Concatenation of two string 2. strcmp() Compares two string 3. strcpy() copies one string over another string 4. strlen() finds the length of the string.

strcat() strcat() : - Using this function you can concat two string: syntax : syntax : strcat(string1,string2); Ex: str1 = Very \0 str2 = Good\0 It also allows to concat three string together Ex: strcat(strcat(str1,str2),str3); output : Very GoodBad str3 = Bad\0 strcat(str1,str2); output : output : Very Good\0

strcmp() : strcmp() : This function compares two string If both are equal then it returns 0 and if they are not equal then it will return numeric difference between the nonmatching character. Ex: Ex: strcmp( their , there ); will return numeric difference between ASCII i and r .

strcpy () : strcpy () : using this function we can copy contents of one string to contents of another string. syntax : strcpy(str1,str2); Ex: Ex: str1 = Very \0 str2 = Good\0 strcpy(str1,str2); will store Good\0 in str1. strlen() : strlen() : This function is used to find the length of the string. n = strlen(string); where n is an integer variable. Ex: Ex: str1 = Very \0 will store 5 to n.