To store the total marks of 100 students an array will be declared as follows,

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1 Chapter 4 ARRAYS LEARNING OBJECTIVES After going through this chapter the reader will be able to declare and use one-dimensional and two-dimensional arrays initialize arrays use subscripts to access individual array elements write programs involving one-dimensional and two-dimensional arrays write programs for matrix operations 4.1 INTRODUCTION Consider the following program main( ) int x ; x = 10; x=15; printf ( x=%d \n,x); This program will print the value of x as 15. Because, when a value 15 is assigned to x, the earlier value of x, i.e., 10 is lost. Thus ordinary variables are capable of holding only one value at a time (as in the above example). However, there are situations in which we would want to store more than one value at a time in a single variable. For example, we wish to arrange the total marks obtained by 100 students in ascending order. To do this, it is needed to store all 100 values in the memory simultaneously. In this situation an array is used. What is an array? An array is a collective name given to a group of related quantities belonging to same data type. These related quantities can be total marks of 100 students or salaries of 500 employees or heights of 200 students. For example, we can use an array name tmarks to represent a set of total marks of a group of 100 students in a class. We can refer to the individual marks by writing a number called index or subscript in square brackets after the array name. Example4.1: To store the total marks of 100 students an array will be declared as follows, float tmarks[100]; tmarks [0], tmarks [1], tmarks [2] etc. represents the total marks of 1 st, 2 nd, 3 rd etc. students. In general, tmarks[i], i can take values 0,1,2,3, represent the total marks of (i+1) th student. Here tmarks is the array name and i is its subscript. Thus the array tmarks is the collection of 100 memory locations referred as below: tmarks[0] tmarks[1] tmarks[2]... tmarks[99] Arrays 87

2 In the above figure, it is assumed that integer value occupies 2 bytes. Thus 200 bytes of space will be allocated to the array tmarks. We can use arrays to represent not only single lists of values but also tables of data(like matrix, marks of 100 students in 6 subjects, sales of a departmental store in a week) in two, three or more dimensions. This chapter explain the use of arrays, types of arrays, declaration and initialization of one dimensional and two dimensional arrays with the help of examples. 4.2 ARRAY DECLARATION Before discussing an array, first of all let us look at the characteristic features of an array i) Array is a data structure storing a group of elements, all of which are of the same data type. ii) All the elements of the array share the same name, and they are distinguished from one another with the help of an index called subscript iii) Random access to every element using a numeric index (subscript) is possible iv) A simple data structure which is extremely useful The declaration of an array is just like any variable declaration with additional size part, indicating the number of elements of the array. Like other variables, arrays must be declared at the beginning of a function. The declaration specifies the data type of the array, the name and its size or dimension Declaration of one dimensional arrays data-type array-name[constant-size] [constant-size]; data-type refers to the type of elements to store and constant-size is the maximum number of elements. The following are some examples of array declarations Example4.2: int x[100]; // x is an array to store maximum 100 integers float height[50]; //height is an array to store heights of maximum 100 persons long int city[50]; //city is an array to store population of maximum 50 cities int fib[15]; //fib is an array to store maximum 15 elements of the fibonacci sequence It is convenient to define array size in terms of a symbolic constant rather than a fixed integer quantity. This makes it easier to modify a program that utilizes an array, since all references to the maximum array size (eg. within for loops as well as in array definitions) can be altered simply by changing the value of the symbolic constant. Example4.3: It is convenient to declare # define SIZE 50; int a[size]; rather than int a[50]; Arrays 88

3 4.3 SUBSCRIPT To refer the elements of an array subscript is used. In an array a with 50 elements, the individual elements are referred by a[0], a[1], a[2],.., a[48], a[49] as shown below: a[0] a[1] a[2] a[48] a[49] Here 0,1,2,3.49 are called subscripts. The sub scripts of an array can be integer constants, integer variables or expressions that yield integers. Example4.4: If we want to represent a set of 5 numbers, say 10, 4, 18, 20, 35 by an array variable a, then we declare the array a as follows: int a[5];and the computer reserve 5 storage locations as follows: a[0] a[1] a[2] a[3] a[4] The values can be assigned to the array elements as follows: a[0] = 10 ; a[1] = 4 ; a[2] = 18 ; a[3] = 20 ; a[4] = 35 ; This could cause the array a to store the values as shown below: a[0] a[1] a[2] a[3] a[4] 4.4 STORAGE OF ONE-DIMENSIONAL ARRAYS IN MEMORY When an array is declared, memory is allocated automatically with respect to its type and size. Array elements are stored in contagious memory locations. For example, a sample layout for the onedimensional integer array a of size 6 elements declared as int a ;is shown below. Address Memory Element number a[0],a[1],a[2], represent the first, second, third etc. elements of the list &a[0],&a[1],&a[2] etc represent the addresses of the first, second, third etc positions of the array Arrays 89

4 4.5 INITIALIZATION OF ARRAY After an array is declared, its elements must be initialized. garbage. An array can be initialized at either of the following stages. Otherwise, they will contain i) At compile time ii) At run time Compile time initialization Arrays can be initialized at the time of declaration. The initial values must appear in the order in which they will be assigned to the individual array elements, enclosed within the braces and separated by commas. Syntax of array initialization is as follows: data type array-name[size]=val1, val2,..., valn; val1 is the value for the first array element, val2 is the value for the second array element, and valn is the value for the n th array element. Example4.5: int = 10, 5, 8, 6, 2; initializes integer array a such that = 10, = 5, a[2]=8, = 6, = 2. Example4.6: char color[5]= G, R, O, B, \0 ; initializes character array color such that color[0]= G, color[1]= R, color[2]= O, color[3]= B color[4]= \0 If the number of initializers in the list is less than the number of elements then only that array elements will be initialized. The remaining elements will be set to zero automatically. Example4.7: int = 10, 5, 8; will initialize the array a such that = 10, = 5, = 8, = 0, = 0. If the number of initializers is more than the array size, then a syntax error would result. Arrays 90

5 Example4.8: int = 10, 5, 8, 12, 7, 14, 20; would result in syntax error. An array can be initialized without specifying the array size. In this case, the number of initializers is used to determine the size of the array. Example4.9: int = 10, 5, 8, 12, 7, 14, 20; would initialize a seven element array of int type Run time initialization An array can be explicitly initialized at run time. Example4.10: Consider the following segment of a C Program. for (i=0; i < 20; ++i) if (i < 5) = 0.0; else = 1.0; The first 5 elements of the array a are initialized to zero while the remaining 15 elements are initialized to 1 at run time. We can also use scanf function to initialize an array. Example4.11: The statements int ; for (i=0; i < 10;++i) scanf ( %d, & ; will initialize the array elements with the values entered through the keyboard. Program 4.1 Program to store n values in an array and display them in reverse order #define SIZE 50 void main( ) int a[size],i,n; printf( Enter the number of values: ); scanf( %d,&n); printf( Enter the values: ); for(i=0; i<n; ++i) scanf( %d,&a[i]); printf( Given values in reverse order is: \n ); for(i=n-1; i>=0; --i) printf( %d\n,a[i]); Arrays 91

6 Program 4.2 Program to find the mean of n values. #include<conio.h> #define SIZE 50 main ( ) float a[size], sum, mean; int n,i; clrscr ( ); printf( Enter the number of values : ); scanf( %d, &n); printf( Enter the values : ); for (i=0; i < n; ++i) scanf( %f, & ); /* find sum */ sum = 0 ; for (i=0; i < n; ++i) sum = sum + ; mean= sum / (float)n ; printf ( Mean of the n values : = % f \n, mean); Program 4.3 Program to arrange a list of numbers in increasing order. To arrange a list of numbers in order is called sorting. Many sorting methods are available in literature. The present program uses a simple sorting method known as Bubble sort. If the list contains n elements, this method require (n-1) passes. In the first pass, adjacent pairs of elements,... are compared and the larger element is pushed down. After the first pass largest element is pushed down to the last location. In the second pass, the pairs of elements,... are compared and the larger element is pushed down. At the end of second pass, second largest element is pushed down to the last but one location. Like this at the end of the (n-1) th pass, entire array will be re-arranged in increasing order. So, a for loop for the operations in p th pass is as follows: for (j=0 ; j< n p ; + + j) if temp = ; = temp; Arrays 92

7 This loop is to be repeated (n-1) times for the values of pass number p=1,2,3,..,(n-1). Thus the program which implements the bubble sort is as follows: #include<conio.h> #define SIZE 50 void main( ) int a[size],n,i,j,temp,p; clrscr( ); printf("enter the number of values in the list: "); scanf("%d",&n); printf("enter the values: "); for(i=0; i<n; ++i) scanf("%d",&a[i]); /*sorting process*/ for(p=1; p<n; ++p) for(j=0; j<n-p; ++j) if(a[j]>a[j+1]) temp=a[j]; a[j]=a[j+1]; a[j+1]=temp; /*output the sorted list*/ printf("the sorted list is: \n"); for(i=0; i<n; ++i) printf("%d\n",a[i]); Program 4.4 Program to search for a specified number in a given list of numbers. Given a list of n numbers, the program will search for a given number say, key in the list. Compare key with,a[n-1], whenever the key match with one of the values of the list stop the comparisons and display a message that the number is found in the list. If the key does not match with any element of the list display the message that the number is not found in the list. # include<stdio.h> # include<conio.h> # define SIZE 50 void main ( ) int i, key, n, flag = 0; int clrscr( ); printf( Enter the number of values in the list: ); scanf( %d, & n); Arrays 93

8 printf( Enter the values : ); for(i=0; i < n; ++i) scanf( %d, & ); printf( Enter the number to be searched: ); scanf( %d, &key); for(i=0; i<n; ++i) if(key = = ) flag = 1; break ; if (flag = = 1) printf( %d is in the list at the position %d \n, key, i+1); else printf ( %d is not in the list \n, key); Program 4.5 Program to merge two sorted lists The two input sorted lists are stored in the arrays a and b respectively. Merged list is stored in array c. Corresponding elements of arrays a and b are compared and the smaller element is copied into the array c. The process is repeated until one of the lists is exhausted,if the elements of array are exhausted then the remaining elements of array a are copied into the array c, This is accomplished by the loop. while (i<m) c[k]=a[i]; ++i ; ++k ; If the elements of array a are exhausted then the remaining elements of array b are copied into c. This is accomplished by the loop while(j<n) c[k]=b[j]; ++j;++k; This procedure is implemented in the following program: #include<conio.h> void main( ) int a[10],b[10],c[20],i,j,k,m,n; printf("enter the number of elements of the first list: "); scanf("%d",&m); printf("enter the elements of the first list: "); for(i=0; i<m; ++i) scanf("%d",&a[i]); printf("enter the number of elements of the second list: "); scanf("%d",&n); Arrays 94

9 for(i=0; i<n; ++i) scanf("%d",&b[i]); i=j=k=0; while(i<m&&j<n) if(a[i]<b[j]) c[k]=a[i]; ++i; else c[k]=b[j]; ++j; ++k; while(i<m) c[k]=a[i]; ++i; ++k; while(j<n) c[k]=b[j]; ++j; ++k; printf("the merged list is: \n ); for(i=0; i<m+n; ++i) printf("%d",c[i]); /*end of main*/ Program 4.6 Program to find the binary representation of decimal integer Divide given decimal integer by 2, remainder is the least significant digit of the binary representation. Take the quotient and divide it by 2,remainder is the next binary digit. Take the new quotient and divide it by 2. Repeat this process till the quotient is zero. The remainders obtained in reverse order are the digits of the binary representation. Since the remainders are to be displayed in reverse order, store them in a one-dimensional array and display them in reverse order. This procedure is implemented in the following program #include<conio.h> void main( ) short int bdigit[[16],nd,num,digit,i=0,j; clrscr(); printf( Enter the decimal number : ); scanf( %d,&num); while(n>0) Arrays 95

10 Program 4.7 digit=n%2; bdigit[i]=digit; ++i; n=n/2; nd=i; for(j=0;j<nd;++j) printf( %d,bdigit[j]); getch(); // nd is the number of digits in binary representation Program to insert an element at a given position in a list. Let the given element be represented by key and the position be represented by pos. Move down all the elements from the given position to the end by one position. Then assign the given elements to a[pos-1]. If the list contains 7 elements and the position to be inserted is 3,then move a[6] to a[7],a[5] to a[6],..a[2] to a[3]. For this, the following code can be used for(i=7;i>=3;--i) a[i]=a[i-1]; Since an element will be inserted, the new list contains one extra element. Therefore increment the value of n by 1. If this increment is done before the moving process, the code for n elements would be ++n; for(i=n-1;i>=pos;--i) a[pos]=key; a[i]=a[i-1]; The program to implement this process is: #include<conio.h> void main( ) int a[10],n,i,key,pos; printf( Enter the number of values in the list: ); scanf( %d,&n); printf( Enter the values ); for(i=0;i<n;++i) scanf( %d,&a[i]); printf( Enter the number to be inserted: ); scanf( %d,&key); printf( Enter the position: ); scanf( %d,&pos); ++n; for(i=n-1;i>=pos;--i) a[i]=a[i-1]; a[pos-1]=key; printf( The new list after insertion is :\n ); Arrays 96

11 for(i=0;i<n;++i) printf( %d\t,a[i]); getch(); Program 4.8 Program to delete an element from the list at a given position. Let the position of element to be deleted be represented by pos. It is not possible to delete an element physically from an array, but it can be overwritten by another number. After reading the value of pos move up all elements of the array from pos to the end. If the list contains 7 elements and the value of pos is 3, the following code can be used to implement this process for(i=2;i<6;++i) a[i]=a[i+1]; Since an element is to be deleted, new list contains n-1 elements only. Therefore the value of n should be decrement by 1. If this decrement is done before the process, the code for n elements would be The program is --n; for(i=pos-1;i<n;++i) a[i]=a[i+1]; #include<conio.h> void main( ) int a[10],i,pos,n; printf( Enter the number of values in the list: ); scanf( %d,&n); printf( Enter the values: ); for(i=0;i<n;++i) scanf( %d,&a[i]); printf( Enter the position: ); scanf( %d,&pos); if(pos<1 pos>n) printf( Invalid position \n ); Arrays 97

12 exit(0); --n; for(i=pos-1;i<n;++i) a[i]=a[i+1]; printf( The newlist after deletion is :\n ); for(i=0;i<n;++i) printf( %d\t,a[i]); getch(); 4.6 TWO-DIMENSIONAL ARRAYS Two-dimensional array is defined as a set of one dimensional arrays each of same size. Twodimensional array is declared in the same manner as one-dimensional arrays. It will require two pairs of square brackets. A two-dimensional array declaration can be written as we have already seen that an n-element, one-dimensional array can be thought of as a list of values. Similarly, an m n, two-dimensional array can be thought of as a table of values having m rows and n columns, as illustrated in the following figure: Row 0 data type array-name [constant-size1] [constant-size2]; Column 0 Column 1 Column 2 Column (n-1) a 0 0 a 0 1 a 0 2 a 0 n 1 a 1 0 a 1 1 a 1 2 a 1 n 1 Row 1 a 2 0 a 2 1 a 2 2 a 2 n 1 Row 2 a m 1 0 a m 2 1 a m 3 2 a m 1 n 1 Row (m-1) Arrays 98

13 Some typical two-dimensional array definitions are shown below. int mat[5][6] ; //mat is an array with 5 rows and 6 columns float sales[6][4] ; //sales is an array with 6 rows and 4 columns 4.7 INITIALIZATION OF TWO-DIMENSIONAL ARRAYS Like the one-dimensional arrays, two-dimensional arrays may be initialized by following their declarations with a list of initial values enclosed in braces. For example, int a[2][3] = 0,0,0,1,1,1; initializes the elements of the first row to zero and the second row to one. The initialization is done row by row and is called row major ordering. The above statement can be equivalently written as int a[2][3] = 0,0,0,1,1,1, by surrounding the elements of each row by braces. When the array is completely initialized with all values, explicitly, we need not specify the row size. That is, the statement int a[ ][3] = 0,0,0, 1, 1, 1; is permitted. If the values are missing in an initialization, they are automatically set to zero. For instance, the statement int a[ 2 ][3] = 1,1, 2; is permitted and will initialize the first two elements of the first row to one, the first element of the second row to two, and all other elements to zero, that is a[0][0]=1 a[0][1]=1 a[0][2]=0 a[1][0]=2 a[1][1]=0 a[1][2]=0 When all the elements are to be initialized to zero, the following short-cut method may be used. int a[3][4] = 0, 0, 0; The first element of each row is explicitly initialized to zero while other elements are automatically initialized to zero. The following statement also will achieve the same result: int a[3][4] = 0; The following initialization of the array will result in syntax error, since the number of values in each inner pair of braces exceeds the defined size of the array. int a[2][3]=1,2,3,4,9,8,6,4,7; Example4.12: To store the elements of a 3x4 matrix in a two-dimensional array a, the array declaration will be Arrays 99

14 int a[3][4]; First row elements are stored in a[0][0],a[0][1],a[0][2] and a[0][3],second row elements are stored in a[1][0], a[1][1], a[1][2] and a[1][3] and third row elements are stored in a[2][0], a[2][1], a[2][2] and a[2][3]. In general, (i+1)th row elements are to be stored in a[i][0],a[i][1],a[i][2] and a[i][3] For this the following loop will be used. for(j=0; j<4; ++j) scanf("%d",&a[i][j]); To store the elements of all the rows, repeat this loop for i=0, 1, 2. Hence the required code is for(i=0; i<3;++i) for(j=0; j<4; ++j) scanf("%d",&a[i][j]); To display the elements of a 3x4 matrix in the natural form first row elements are to be displayed on the first line, second row elements are on second line and third row elements on third line. For this the following code can be used. for(i=0; i<3;++i) for(j=0; j<4; ++j) printf("%8d",a[i][j]); printf( \n ); Program 4.9 Program to add two matrices Given two matrices A of order r1 c1 and B of order r2 c2, we write a program to find their sum with suitable validation. To find the sum matrix we have to find each element of the sum matrix.in general (i,j)th element of the sum matrix C is obtained as C[i][j]= A[i][j] + B[i][j]; for all combinations of i=0,1,2,,r1-1 and j=0,1,2,c1-1. /*Program to find sum of two matrices*/ Arrays 100

15 #include<conio.h> #include <stdlib.h> #define ROWSIZE 5 #define COLSIZE 5 void main ( ) int r1, c1, r2, c2, i,j; int a[rowsize] [COLSIZE], b[rowsize] [COLSIZE],c[ROWSIZE] [COLSIZE]; printf ( Enter the number of rows and columns of first matrix: ); scanf ( %d %d, & r1, & c1); printf ( Enter the number of rows and columns of second matrix: ); scanf ( %d %d, & r2, & c2); if printf ( Given matrices are not of same order and hence addition is not possible \n ); exit (0); printf ( Enter the elements of the first matrix row wise : \n ); for (i=0 ; i < r1 ; ++i) for (j=0 ; j < c1 ; ++j) scanf ( %d, & ; printf ( Enter the elements of the second matrix row wise:\n ); for (i=0; i < r2 ; + + i) for (j=0; j < c2 ; + + j) scanf ( %d, & b ; /* add the two matrices*/ for (i=0 ; i < r1 ; ++i) for (j=0 ; j < c1 ; ++j) Arrays 101

16 /*output the sum matrix */ printf The sum matrix is : \n ); for (i=0; i < r1 ; ++i) for (j=0; j< c1 ; ++j) printf ( %8d, ; printf( \n ); /*end of main*/ Program 4.10 Program to find the product of two matrices The following procedure will be used to find the product. If A is a matrix of order m p and B is a matrix of order p n, then the (i, j) th element of the product matrix is obtained by c ij a io ai 1 ai2... a ip 1 b b b b j j j P 1 j =[a i0 b 0j +a i1 b 1j +a i2 b 2j + +a ip-1 b p-1j ] = p 1 k 0 a ik b kj Thus, the following loop can be used to find the (i, j) th element for (k = 0 ; k < p ; ++k) /*Program to find the product of two matrices*/ Arrays 102

17 #include<conio.h> #include<stdlib.h> #define ROWSIZE 5 #define COLSIZE 5 void main ( ) int i, j,k, r1, c1, r2, c2 ; int a[rowsize] [COLSIZE], b[rowsize] [COLSIZE],c[ROWSIZE] [COLSIZE]; printf ( Enter the order of the first matrix : ); scanf ( %d%d, &r1, &c1); printf ( Enter the order of the second matrix : ); scanf (%d%d, &r2, &c2); if (c1! = r2) printf ( product of given matrices does not exist \n ); exit (0); printf ( Enter the elements of first matrix row wise : \n ); for (i=0; i < r1 ; ++i) for (j=0; j < c1; ++j) scanf( %d, &a printf( Enter the elements of second matrix column wise:\n ); for(i=0; i<r2; ++i) for (j=0; j< c2; ++j scanf( %d, & b /*find the elements of product matrix*/ for(i=0; i<r1; ++i) for (j=0; j < c2; ++j) Arrays 103

18 c[i][j] = 0; for(k=0; k<c1; ++k) c[i][j] + = ; printf ( The product matrix is : \n ); for (i=0; i< r1; ++i) for (j=0; j< c2; ++j) printf ( %8d, c[i][j] ); printf( \n ); /*end of main */ Program4.11 Program to check a given square matrix is symmetric The matrix A=[a ij ] n m is symmetric if a ij =a ji for all combinations of i and j Hence, check the condition a ij =a ji for i=0,1,2,..n-2 and j=i+1,i+2, n-1. If any one pair of elements is unequal, the matrix is not symmetric #include<conio.h> void main ( ) int n,a[5][5],i,j,flag=0; printf ( Enter the order of the square matrix : ); scanf ( %d, &n); printf ( Enter the elements of first matrix row wise : \n ); for (i=0; i < n ; ++i) for (j=0; j < n; ++j) scanf( %d, &a Arrays 104

19 for(i=0;i<n-1;++i) for(j=i+1;j<n;++j) if(flag) if(a[i][j]!=a[j][i]) flag=1; break; if(flag==1) break; printf( \n Given matrix is not symmetric ); else printf( \n Given matrix is symmetric ); getch(); Note that, if any pair of elements are unequal, 1 is assigned to flag and break is executed. Since this break statement is in the inner loop only that loop execution is terminated. Hence the value of flag must be compared with 1 in the outer loop. Program4.12 Programto displayn linesof the Pascal triangle. When n=6, the triangle is as follows In each row, first and last elements are 1 s. In general i th row elements are obtained as follows: a[i][0]=a[i][i]=1 a[i][j]=a[i-1][j-1]+a[i-1][j], j=1,2,.(i-1) Arrays 105

20 Repeat this for i=0,1,2..n-1 The program which implement this procedure is : #include<conio.h> void main ( ) int a[10][10],i,j,n; printf ( Enter the value of n: ); scanf ( %d, &n); for(i=0;i<n;++i) a[i][0]=a[i][i]=1; for(j=1;j<i;++j) a[i][j]=a[i-1][j-1]+a[i-1][j]; printf( The pascal triangle is: \n ); for(i=0;i<n;++i) for(j=0;j<40-3*i;++j) //To leave 40-3i blanks in the line printf( ); for(j=0;j<=i;++j) printf( %3d,a[i][j]); Program4.13 Given the roll number and marks in three subjects of 100 students, write a program to determine the following: i. Total marks obtained by each student ii. The highest marks in each subject and the roll no, of the student who secured it. iii. The student who obtained the highest total marks. Store the roll numbers in a one dimensional integer array rno, marks in a two dimensional array m of size 100 4, where total marks are stored in 4 th column. Find the sum of marks in each row for total Arrays 106

21 marks, maximum marks in the first three columns for subject wise maximum and maximum marks in fourth column for highest total marks. Display the output in a tabular form #include<conio.h> void main ( ) int rno[100],i,s1_rno,s2_rno,s3_rno,total_rno; float m[100][4], s1_max,s2_max,s3_max,total_max; printf( Enter the Roll no. and marks in 3 subjects of 100 students: \n ); for(i=0;i<100,++i) scanf( %d%f%f%f,&rno[i],&m[i][0],&m[i][1],&m[i][2]); /* To find total marks of each student */ for(i=0;i<100;++i) m[i][3]=m[i][0]+m[i][1]+m[i][2]; /* To find subject wise maximum marks and the roll numbers of the students who secured them */ s1_max=m[0][0]; s2_max=m[0][1]; s3_max=m[0][2]; total_max=m[0][3]; s1_rno=rno[0]; s2_rno=rno[0]; s3_rno=rno[0]; total_rno=rno[0]; for(i=1;i<100;++i) if(s1_max<m[i][0]) s1_max=m[i][0]; s 1 _rno=rno[i]; Arrays 107

22 if(s2_max<m[i][1]) s2_max=m[i][1]; s2_rno=rno[i]; if(s3_max<m[i][2]) s3_max=m[i][2]; s3_rno=rno[i]; if(total_max<m[i][3]) total_max=m[i][3]; total_rno=rno[i]; printf( \n\t Roll no \t Sub1 \t Sub2 \t Sub3 \t Total\n ); for(i=0;i<100;++i) printf( \t %d \t %6.2f \t %6.2f \t %6.2f \t %6.2f \n,rno[i],m[i][0],m[i][1],m[i][2]); printf( Maximum marks in subject 1 is %6.2f and the roll number of the student is %d \n, s1_max,s1_rno); printf( Maximum marks in subject 2 is %6.2f and the roll number of the student is %d \n, s2_max, s2_rno); printf( Maximum marks in subject 3 is %6.2f and the roll number of the student is %d \n, s3_max, s3_rno); printf( Highest total marks is %6.2f and the roll number of the student is %d \n, total_max, total_rno); getch(); Arrays 108

23 SUMMARY EXERCISES C uses arrays as a way of describing a collection of data items with identical properties. The group has a single name for all its members, with the individual member being selected by an index. We have learnt in this unit, the basic purpose of using an array in the program, declaration of array and assigning values to the arrays. All elements of the arrays are stored in the contagious memory locations. Without exception, all arrays in C are indexed from 0 up to one less than the bound given in the declaration. One important point about array declaration is that they don t permit the use of varying subscripts. The numbers given must be constant expressions which can be evaluated at compile time, not run time. Global and static array elements are initialized to 0 by default, and automatic array elements are filled with garbage values. C never check whether the array index is valid either at compile time or when the program is running. Single operations, which involve entire arrays, like copying one array into another array, input or output of all the elements of the array without subscripts are not permitted in C. Multiple choice Questions: 4.1.What is the output when the following program segment is executed? int a[5]=71,82,69,69,78; for(i=0;i<5;++i) printf( %c,a[i]) a) GREEN b) c)fqddm d) ISFFO 4.2. What is the output when the following code is executed? void main() int arr[6]=12,13; printf( \n %d, %d,a[1],a[3]); a)13,garbage b)12,13 c)12,garbage d)13,0 4.3.Array name is a)an array variable b)a key word c)a common name shared by all elements d)not used in a program Arrays 109

24 4.4. Array elements occupy a)adjacent memory locations b)random location for each element c)varying length of memory locations for each element. d) no space in memory Array is used to represent a)a list of data items of integer data type. b) a list of data items of real data type. c) a list of data items of different data type. d) a list of data items of same data type Array subscripts in C always starts at a)-1 b)0 c)1 d)any value 4.7.If the size of the array is less than the number of initializes, then a) extra values are neglected b) it is an error c) the size is automatically increased d) the size is neglected What is the output when the following program is executed? main() int a[5]=1,2,3,4,5,sum=0,i=0 begin: sum+=a[i]; ++i; if(i<5) goto begin; printf( %d,sum); Arrays 110

25 a) 10 b) 1 c) 15 d) What is the output when the following program is executed? main() int a[5] = 1,3,4, i ; for ( i = 4; i> = 0; --i ) printf ( %d \t, a[i]); a) b) c) d) syntax error will occur during execution of the program What is the output when the following program is executed? main() int a[5], i; for( i=0; i < 5; ++i) a[i] = i * i ; for( i=0; i< 5 ; ++i) printf( %d, a[i]); a) b) c) d) What is the output when the following program is executed? main() int a[5] = 3,1, 10, 20, 30,i=0,x,y,z; x = ++a[1]; y = a[i++]; z = a[i]++; printf( x= %d, y = %d, z = %d \n, x, y, z ); a)x=2,y=3,z=1 b) x=4,y=3,z=1 c) x=4,y=1,z=2 d) x=3,y=3,z= Identify the error in the following code. main() Arrays 111

26 int a[5]=9,11,3,6,4,b[5],i; b=a; for(i=0;i<5;++i) printf( \n %d,b[i]); a) variable subscript i is not allowed b) since the array b is not initialized we cannot display the values of the array b c) one array cannot be assigned to another array using assignment operator d) array cannot be initialized in the type declaration statement What is the output generated by the following program segment. int a, b = 0 ; int c[10] = 1,2,3,4,5,6,7,8,9,0; for(a=0; a < 10 ; + + a) if b + = c ; printf( b = %d, b); a) b= 25 b) b= 20 c)b=45 d) What is the output generated by the following program segment? int a, b = 0 ; int c[10] = 1,2,3,4,5,6,7,8,9,0; for(a=0 ; a < 10 ; ++a) if((c[a]%2)= = 0) b + = ; printf( b=%d, b); a) b= 25 b) b= 20 c)b=45 d) What is the output generated by the following program segment? int i ; int a[5]=0; Arrays 112

27 for(i = 1; i < 5 ; ++i) = i + for(i = 0 ; i < 5 ; ++i) printf ( %d \t, ) ; a) b) c) d) unpredictable output What is the output generated by the following program segment? int a, b, c ; int x [3] [4] = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12; for(a=0; a < 3 ; ++a) c = 999 ; for (b=0 ; b < 4 ; ++b) if ( c =x ; printf ( %3d, c); a) b) c) d) What will be the output of the flowing program? int main() int arr[5], i=0; while(i<5) arr[i]=++i; for(i=0; i<5; i++) printf("%d\t ", arr[i]); return 0; a) b)garbage c) d) What is the output if the flowing program is executed? Arrays 113

28 main() int x[10],i,sum=0; for(i=0;i<10;i+=3) x[i]=i; sum=sum+x[i]; printf( %d \n,sum); a) 55 b) 45 c) 65 d)unpredictable output Comprehensive Questions: 4.1 Write a program to rearrange the elements of an array in reverse order without using a second array 4.2 Write a C program to find the binary equivalent of an integer number using array 4.3 Write a program to find median of a set of numbers 4.4 Write a program to compare two one dimensional arrays containing two sets of numbers 4.5 Write a program to find the median height of students in a section 4.6 Write a program to implement the binary search 4.7 A list of failed registered numbers of students is stored in an array. Write a program to determine whether a given register number is in the list using linear search 4.8 Write a program for fitting a straight line through a set of points (x i, y i ), i =1,2,... n. The straight line equation is y = mx + c and the values of m and c are given by All summations are from 1 to n. Arrays 114

29 4.9 Given a list of 200 integers each of them ranges from 0 to 10 write a program to count the number of occurrences of each character 4.10 The annual examinations results of 100 students are tabulated as follows: Roll No. Subject 1 Subject 2 Subject Write a program to read the data and determine the following: a) Total marks obtained by each student b) The highest marks in each subject and the Roll No. of the student who secured it. c) The student who secured the highest total marks Write a program to find the transpose of a matrix 4.12 Write a program to find the trace of a matrix 4.13 Write a program to check if a given matrix is symmetric 4.14 Write a program to sort the elements of each row of a matrix in ascending order 4.15 Write a program that fills a five-by-five matrix as follows: i. Upper left triangle with 1s ii. Lower right triangle with -1s iii. Right to left diagonal with zeros Display the contents of the matrix Write a program to find the transpose of a matrix without using additional array 4.17 Write a program to check if a given matrix is upper triangular 4.18 Write a program to input 10 integers and sort them. Use a menu system to determine whether the sort should be ascending or descending order. Also determine whether the elements have to be sorted by their actual value or absolute value. The process should continue till the user desires to exit. Arrays 115