C program

K & R C Chapter 3 Exercise Solutions

Posted on 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

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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 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 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.

/***********************************************************
* You can use all the programs on  www.c-program-example.com
* for personal and learning purposes. For permissions to use the
* programs for commercial purposes,
* contact [email protected]
* To find more C programs, do visit www.c-program-example.com
* and browse!
* 
*                      Happy Coding
***********************************************************/

#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 = '';
    
    pointer = start;
    strcpy(string, pointer); /* If you wish to convert original string */
    free(pointer);
    
    printf("String after removing vowels is "%s"n", string);
    
    return 0;
}

int check_vowel(char a)
{
    if ( a >= 'A' && a <= 'Z' )
    a = a + 'a' - 'A';
    
    if ( a == 'a' || a == 'e' || a == 'i' || a == 'o' || a == 'u')
    return TRUE;
    
    return FALSE;
}
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C Program to delete a file.

Posted on by Sandeepa Nadahalli
Write a C Program to delete a file.
To delete a file in c, We use the remove macro, which is defined in stdio.h. remove macro takes filename with extension as its argument and deletes the file, if it is in the directory and returns the zero, if deleted successfully.
Note that deleted file does not goes to the recycle bin, it is going to delete permanently.
Read more about C Programming Language . and read the C Programming Language (2nd Edition). by K and R.

/***********************************************************
* You can use all the programs on  www.c-program-example.com
* for personal and learning purposes. For permissions to use the
* programs for commercial purposes,
* contact [email protected]
* To find more C programs, do visit www.c-program-example.com
* and browse!
* 
*                      Happy Coding
***********************************************************/

#include<stdio.h>
#include<conio.h>
#include<process.h>
main()
{
    FILE *fp;
    char filename[20];
    int status;
    clrscr();
    printf("nEnter the file name:nn");
    scanf("%s",filename);
    
    fp = fopen(filename, r);
    
    if(fp == NULL)
    {
        printf("Error:  file not found! check the directory!!nn");
        exit(0);
    }
    fclose(fp);
    status = remove(file_name);
    
    if( status == 0 )
    printf("%s file deleted successfully.n",file_name);
    else
    {
        printf("Unable to delete the filen");
        perror("Error");
    }
    
    return 0;
}
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C Program to demonstrate strspn function.

Posted on by Sandeepa Nadahalli
Write a C Program to demonstrate strspn function.
The strspn() function returns the index of the first character in string1 that doesn’t match any character in string2. If all the characters of the string2 matched with the string1, strspn returns the length of the string1. Read more about C Programming Language .

/***********************************************************
* You can use all the programs on  www.c-program-example.com
* for personal and learning purposes. For permissions to use the
* programs for commercial purposes,
* contact [email protected]
* To find more C programs, do visit www.c-program-example.com
* and browse!
* 
*                      Happy Coding
***********************************************************/

#include<stdio.h>
#include<string.h>
#include<conio.h>
int main()
{
    int spn;
    char str1[] = "1234hjbcde09i";
    char str2[] = "12345";
    char str3[] = "a12d3456fd";
    char char_list[] = "1234567890";
    clrscr();
    //It returns 4
    spn = strspn (str1,char_list);
    printf ("nnThe length of the initial numbers for str1 is %d.n",spn);
    
    //It returns 5
    spn = strspn (str2,char_list);
    printf ("nThe length of the initial numbers for str2 is %d.n",spn);
    
    //It returns 0
    spn = strspn (string3,char_list);
    printf ("nThe length of the initial numbers for string3 is %d.n",spn);
    return 0;
}

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C program to demonstrate ceil function.

Posted on by Sandeepa Nadahalli
Write a C program to demonstrate ceil function.ceil is in the C math.h library.
ceil function rounds up the smallest next integral value.
Example:ceil(2.0) is 2.0
ceil(2.1) is 3.0
ceil(2.2) is 3.0
—
—
ceil(2.9) is 3.0
Read more about C Programming Language.

/***********************************************************
* You can use all the programs on  www.c-program-example.com
* for personal and learning purposes. For permissions to use the
* programs for commercial purposes,
* contact [email protected]
* To find more C programs, do visit www.c-program-example.com
* and browse!
* 
*                      Happy Coding
***********************************************************/




#include<stdio.h>
#include<math.h>
#include<conio.h>
int main()
{
    double number, result;
    clrscr();
    printf("Enter a number to round it upn");
    scanf("%lf",&number);
    
    result = ceil(number);
    
    printf("nOriginal number =  %lfn", number);
    printf("nNumber rounded up = %lfn", result);
    getch();
    return 0;
} 
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C program to draw a circle using c graphics.

Posted on by Sandeepa Nadahalli
Write C program to draw a circle using c graphics.
In this program we use the graphics.h library function to draw a circle. To use graphics.h, we have to install the drivers in to the the system by using the initgraph() function. In the program circle is the graphic function , which takes three parameters, first two are co-ordinates and the third one is the radius of the circle. Read more about C Programming Language.

/***********************************************************
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* for personal and learning purposes. For permissions to use the
* programs for commercial purposes,
* contact [email protected]
* To find more C programs, do visit www.c-program-example.com
* and browse!
* 
*                      Happy Coding
***********************************************************/

#include <graphics.h>

main()
{
    int gd = DETECT, gm;
    initgraph(&gd, &gm, "C:\TC\BGI");
    
    circle(25, 25, 100);
    
    getch();
    closegraph();
    return 0;
}
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C Program to compute the difference between two dates.

Posted on by Sandeepa Nadahalli
Write a C program to compute the difference between two dates.In this C Program, We check the date is valid or not and then calculating the No. of days of first date and second date from Jan 1 of first date, then subtract the smaller date from another. Read more about C Programming Language .

/***********************************************************
* You can use all the programs on  www.c-program-example.com
* for personal and learning purposes. For permissions to use the
* programs for commercial purposes,
* contact [email protected]
* To find more C programs, do visit www.c-program-example.com
* and browse!
* 
*                      Happy Coding
***********************************************************/

#include<stdio.h>
#include<math.h>
#include<conio.h>
void main()
{
    int day1,mon1,year1,day2,mon2,year2;
    int ref,dd1,dd2,i;
    clrscr();
    printf("Enter first date  day, month, yearn");
    scanf("%d%d%d",&day1,&mon1,&year1);
    printf("Enter second date day, month, yearn");
    scanf("%d%d%d",&day2,&mon2,&year2);
    ref = year1;
    if(year2<year1)
    ref = year2;
    dd1=0;
    dd1=dater(mon1);
    for(i=ref;i<year1;i++)
    {
        if(i%4==0)
        dd1+=1;
    }
    dd1=dd1+day1+(year1-ref)*365;
    dd2=0;
    for(i=ref;i<year2;i++)
    {
        if(i%4==0)
        dd2+=1;
    }
    dd2=dater(mon2)+dd2+day2+((year2-ref)*365);
    printf("nn Difference between the two dates is %d days",abs(dd2-dd1));
    
    getch();
}




int dater(x)
{ int y=0;
    switch(x)
    {
        case 1: y=0; break;
        case 2: y=31; break;
        case 3: y=59; break;
        case 4: y=90; break;
        case 5: y=120;break;
        case 6: y=151; break;
        case 7: y=181; break;
        case 8: y=212; break;
        case 9: y=243; break;
        case 10:y=273; break;
        case 11:y=304; break;
        case 12:y=334; break;
        default: printf("Invalid Inputnnnn"); exit(1);
    }
    return(y);
}

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C program to replace the sub string with another string.

Posted on by Sandeepa Nadahalli
C Strings:
Write a C program to replace the sub string in a string with another string.
In this program, We replace string with another string, if the entered string is the sub string of main string, otherwise function replace_str returns the original string as it is. Read more about C Programming Language . 

/***********************************************************
* You can use all the programs on  www.c-program-example.com
* for personal and learning purposes. For permissions to use the
* programs for commercial purposes,
* contact [email protected]
* To find more C programs, do visit www.c-program-example.com
* and browse!
* 
*                      Happy Coding
***********************************************************/

#include <stdio.h>
#include <string.h>

char *replace_str(char *str, char *orig, char *rep)
{
    static char buffer[4096];
    char *p;
    
    if(!(p = strstr(str, orig)))
    return str;
    
    strncpy(buffer, str, p-str);
    buffer[p-str] = '';
    
    sprintf(buffer+(p-str), "%s%s", rep, p+strlen(orig));
    
    return buffer;
}

int main(void)
{
    char str[100],str1[50],str2[50];
    printf("Enter a one line string..n");
    gets(str);
    printf("Enter the sub string to be replaced..n");
    gets(str1);
    printf("Enter the replacing string....n");
    gets(str2);
    puts(replace_str(str, str1, str2));
    
    return 0;
}
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C Program to find all the permutations of a given string.

Posted on by Sandeepa Nadahalli
Write a c program to find all the permutations of a given string.
Example: If the given string is sam, output is,
sam
sma
msa
mas
asm
ams.
Read more about C Programming Language . 

/***********************************************************
* You can use all the programs on  www.c-program-example.com
* for personal and learning purposes. For permissions to use the
* programs for commercial purposes,
* contact [email protected]
* To find more C programs, do visit www.c-program-example.com
* and browse!
* 
*                      Happy Coding
***********************************************************/

# include<stdio.h>
# include<conio.h>
#include<string.h>
void swap (char *x, char *y)
{
    char temp;
    temp = *x;
    *x = *y;
    *y = temp;
}

void permute(char *a, int i, int n)
{
    int j;
    if (i == n)
    printf("%sn", a);
    else
    {
        for (j = i; j <= n; j++)
        {
            swap((a+i), (a+j));
            permute(a, i+1, n);
            swap((a+i), (a+j));
        }
    }
}


int main()
{
    char str[80] ;
    int len=0,i;
    puts("Enter a string:nn");
    gets(str);
    for (i=0; str[i] != ''; i++)
    {
        len++;
    }
    permute(str, 0, len);
    getchar();
    return 0;
}
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