K & R C Chapter 3 Exercise Solutions

Posted on April 16, 2012 by Sandeepa Nadahalli

We have already provided solutions to all the exercises in the book “C Programming Language (2nd Edition)“ popularly known as K & R C book.

In this blog post I will give links to all the exercises from Chapter 3 of the book for easy reference.

Chapter 3: Control Flow

Exercise 3-1. Our binary search makes two tests inside the loop, when one would suffice (at the price of more tests outside). Write a version with only one test inside the loop and measure the difference in run-time.
Solution to Exercise 3-1.

Exercise 3-2.Write a function escape(s,t) that converts characters like newline and tab into visible escape sequences like n and t as it copies the string t to s . Use a switch . Write a function for the other direction as well, converting escape sequences into the real characters.
Solution to Exercise 3-2.

Exercise 3-3.Write a function expand(s1,s2) that expands shorthand notations like a-z in the string s1 into the equivalent complete list abc…xyz in s2 . Allow for letters of either case and digits, and be prepared to handle cases like a-b-c and a-z0-9 and -a-z . Arrange that a leading or trailing – is taken literally.
Solution to Exercise 3-3.

Exercise 3-4.In a two’s complement number representation, our version of itoa does not handle the largest negative number, that is, the value of n equal to -(2 to the power (wordsize – 1)) . Explain why not. Modify it to print that value correctly regardless of the machine on which it runs.
Solution to Exercise 3-4.

Exercise 3-5. Write the function itob(n,s,b) that converts the integer n into a base b character representation in the string s . In particular, itob(n,s,16) formats n as a hexadecimal integer in s
Solution to Exercise 3-5.

Exercise 3-6. Write a version of itoa that accepts three arguments instead of two. The third argument is a minimum field width; the converted number must be padded with blanks on the left if necessary to make it wide enough.
Solution to Exercise 3-6.

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C Program to check matrix is magic square or not

Posted on April 13, 2012September 6, 2017 by Sandeepa Nadahalli

Write a c program to check whether the given matrix is a magic square matrix or not.

A matrix is magic square matrix, if all rows sum, columns sum and diagonals sum are equal.

Example:
8   1 6
3   5   7
4   9 2

is the magic square matrix. As you can see numbers in first row add up to 15 (8 + 1 + 6), so do the numbers of 2nd row 3 + 5 + 7. Also the number in the last row 4 + 9 + 2. Similarly, the columns all add up to the same number 15. Hence, this matrix is a magic square matrix.

The Program

  
          #include <stdio.h>
        
          void main() {
        
          	int A[50][50];
        
          	int i, j, M, N;
        
          	int size;
        
          	int rowsum, columnsum, diagonalsum;
        
          	int magic = 0;
        
          	printf("Enter the order of the matrix:\n");
        
          	scanf("%d %d", &M, &N);
        
          	if(M==N) {
        
          		printf("Enter the elements of matrix \n");
        
          		for(i=0; i<M; i++) {
        
          			for(j=0; j<N; j++) {
        
          				scanf("%d", &A[i][j]);
        
          			}
        
          		}
        
          		printf("\n\nMATRIX  is\n");
        
          		for(i=0; i<M; i++) {
        
          			for(j=0; j<N; j++) {
        
          				printf("%3d\t", A[i][j]);
        
          			}
        
          			printf("\n");
        
          		}
        
          		// calculate diagonal sum 
        
          		diagonalsum = 0;
        
          		for(i=0; i<M; i++) {
        
          			for(j=0; j<N; j++) {
        
          				if(i==j) {
        
          					diagonalsum = diagonalsum + A[i][j];
        
          				}
        
          			}
        
          		}
        
          		// calculate row sum
        
          		for(i=0; i<M; i++) {
        
          			rowsum = 0;
        
          			for(j=0; j<N; j++) {
        
          				rowsum = rowsum + A[i][j];
        
          			}
        
          			if(rowsum != diagonalsum) {
        
          				printf("\nGiven matrix is not a magic square");
        
          				return;
        
          			}
        
          		}
        
          		// calculate column sum
        
          		for(i=0; i<M; i++) {
        
          			columnsum = 0;
        
          			for(j=0; j<N; j++) {
        
          				columnsum =  columnsum + A[j][i];
        
          			}
        
          			if(columnsum != diagonalsum) {
        
          				printf("\nGiven matrix is not a magic square");
        
          				return;
        
          			}
        
          		}
        
          		printf("\nGiven matrix is a magic square matrix");
        
          	} else {
        
          		printf("\n\nPlease enter the square matrix order(m=n) \n\n");
        
          	}
        
          }

view raw magic_square.c hosted with ❤ by GitHub

Sample Output

Read more about C Programming Language and read the C Programming Language (2nd Edition). by K and R.

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C Program to delete vowels in a string.

Posted on April 11, 2012 by Sandeepa Nadahalli

C Strings:
Write a C Program to delete a vowel in a given string.
In this program, We use the pointers to position the characters.check_vowel() function checks the character is vowel or not, if the character is vowel it returns true else false.
Example output:Given string: Check vowel
Output is: Chck vwl
Read more about C Programming Language . and read the C Programming Language (2nd Edition). by K and R.

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* and browse!
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***********************************************************/

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<conio.h>
#define TRUE 1
#define FALSE 0

int check_vowel(char);

main()
{
    char string[100], *temp, *pointer, ch, *start;
    csrcscr();
    printf("nnEnter a stringn");
    scanf("%s",string);
    temp = string;
    pointer = (char*)malloc(100);

    if( pointer == NULL )
    {
        printf("Unable to allocate memory.n");
        exit(EXIT_FAILURE);
    }

    start = pointer;

    while(*temp)
    {
        ch = *temp;

        if ( !check_vowel(ch) )
        {
            *pointer = ch;
            pointer++;
        }
        temp++;
    }
    *pointer = '

	#include <stdio.h>
	void main() {
	int A[50][50];
	int i, j, M, N;
	int size;
	int rowsum, columnsum, diagonalsum;
	int magic = 0;

	printf("Enter the order of the matrix:\n");
	scanf("%d %d", &M, &N);
	if(M==N) {
	printf("Enter the elements of matrix \n");
	for(i=0; i<M; i++) {
	for(j=0; j<N; j++) {
	scanf("%d", &A[i][j]);
	}
	}

	printf("\n\nMATRIX is\n");
	for(i=0; i<M; i++) {
	for(j=0; j<N; j++) {
	printf("%3d\t", A[i][j]);
	}
	printf("\n");
	}

	// calculate diagonal sum
	diagonalsum = 0;
	for(i=0; i<M; i++) {
	for(j=0; j<N; j++) {
	if(i==j) {
	diagonalsum = diagonalsum + A[i][j];
	}
	}
	}

	// calculate row sum
	for(i=0; i<M; i++) {
	rowsum = 0;
	for(j=0; j<N; j++) {
	rowsum = rowsum + A[i][j];
	}
	if(rowsum != diagonalsum) {
	printf("\nGiven matrix is not a magic square");
	return;
	}
	}

	// calculate column sum
	for(i=0; i<M; i++) {
	columnsum = 0;
	for(j=0; j<N; j++) {
	columnsum = columnsum + A[j][i];
	}
	if(columnsum != diagonalsum) {
	printf("\nGiven matrix is not a magic square");
	return;
	}
	}

	printf("\nGiven matrix is a magic square matrix");
	} else {
	printf("\n\nPlease enter the square matrix order(m=n) \n\n");
	}
	}