Print Reverse of a string using Recursion

Print reverse of a  string using recursion:

# include <stdio.h>

/* Function to print reverse of the passed string */
void reverse(char *str)
{
   if(*str)
   {
       reverse(str+1);
       printf("%c", *str);
   }
}

int main() 
{
   char a[] = "Tech Stuff for Interview";
   reverse(a);
   return 0;
}

Explanation: Recursive function (reverse) takes string pointer (str) as input and calls itself with next location to passed pointer (str+1). Recursion continues this way, when pointer reaches ‘\0′, all functions accumulated in stack print char at passed location (str) and return one by one.

Programme for getting IP address information

# C Programme for Getting IP Address Information Using Network Interfacing

#include <stdio.h>
#include <string.h> /* for strncpy */
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <netinet/in.h>
#include <net/if.h>

int main()
{
 int fd;
 struct ifreq ifr;

 fd = socket(AF_INET, SOCK_DGRAM, 0);

 /* I want to get an IPv4 IP address */
 ifr.ifr_addr.sa_family = AF_INET;

 /* I want IP address attached to "eth0" */
 strncpy(ifr.ifr_name, "eth0", IFNAMSIZ-1);

 ioctl(fd, SIOCGIFADDR, &ifr);

 close(fd);

 /* display result */
 printf("%s\n", inet_ntoa(((struct sockaddr_in *)&ifr.ifr_addr)->sin_addr));

 return 0;
}

Multiline macros in C

Multi Line Macro in C

We can write multi line macro same like function but each statement ends with "\". Below is the simple macro , which accepts input number from user, and prints whether entered number is even or odd.

#include <stdio.h>

#define MACRO(num, str) ({\
            printf("%d", num);\
            printf(" is");\
            printf(" %s number", str);\
            printf("\n");\
           })

int main(void)
{
    int num;
    printf ("Enter no\n");
    scanf("%d", &num);

    if (num & 1)
        MACRO(num, "Odd");
    else
        MACRO(num, "Even");

    return 0;
}


Output:

#cc     macro.c   -o macro
#./macro

#Enter a number: 10

#10 is Even number

How to create Zombie Process IN Linux

Zombie Process:

On Unix and Unix-like computer operating systems, a Zombie process or defunct process is a process that has completed execution but still has an entry in the process table. This entry is still needed to allow the parent process to read its child's exit status

#include<stdio.h>
#include<sys/types.h>
#include<unistd.h>
#include<sys/wait.h>
int main()
{
int id ,x ,y;
id=fork();
if(id==0)
{
x=getpid();
y=getppid();            // in this progtamme first parent execute then child. in parent sleeping for 15ms and child for 5                          ms. in 5 ms child process finish so it create zombie process
printf("Child process 1>PID:%d child 2>PPID:%d\n",x,y);
sleep(5);
printf("\nchild terminated\n");
}
else{
x=getpid();
y=getppid();
printf("Parent process 1>PID:%d parent 2>PPID:%d\n",x,y);
sleep(15);
//wait(&id);
printf("\nparent terminated\n");
}
return(0);
}


Output:


Parent process 1>PID:5307 parent 2>PPID:2588
Child process 1>PID:5308 child 2>PPID:5307

child terminated

parent terminated

Rotate bits of a Numbers

Left and Right Rotation of BIT:     


#include <stdio.h>
#define BIT 32
int leftrotate(int n,int d)
{
        return (n<<d)|(n>>(BIT-d));
}
int rightrotate(int n,int d)
{
        return (n>>d)|(n<<(BIT-d));
}
int main()
{
        int n,d;
        printf ("Enter no\n");
        scanf ("%d",&n);
        printf ("how many bit left rotate\n");
        scanf ("%d",&d);
        printf (" left rotation of %d by %d is ",n,d);
        printf ("%d\n",leftrotate(n,d));
        printf (" right rotation of %d by %d is ",n,d);
        printf ("%d\n",rightrotate(n,d));
}

output:

Enter no

4

how many bit left rotate

2

 left rotation of 4 by 2 is 16

 right rotation of 4 by 2 is 1

Print Reverse of a string using Recursion

Print reverse of a  string using recursion:

# include <stdio.h>

/* Function to print reverse of the passed string */
void reverse(char *str)
{
   if(*str)
   {
       reverse(str+1);
       printf("%c", *str);
   }
}

int main() 
{
   char a[] = "Tech Stuff for Interview";
   reverse(a);
   return 0;
}

C program to print all permutations of a given string

C program to print all permutations of a given string:

# include <stdio.h>
void swap (char *x, char *y)                //swap values at two pointers
{
    char temp;
    temp = *x;
    *x = *y;
    *y = temp;
}
void permute(char *a, int i, int n)

{
   int j;
   if (i == n)
     printf("%s\n", a);
   else
   {
        for (j = i; j <= n; j++)
       {
          swap((a+i), (a+j));
          permute(a, i+1, n);
          swap((a+i), (a+j));                 //backtrack
       }
   }
}

int main()
{
   char a[] = "ABC";
   permute(a, 0, 2);
   return 0;
}

ASCII Table

Add caption

  

Implement Your Own sizeof Function

Implement Your Own sizeof () function:

#define my_sizeof(type) (char *)(&type+1)-(char*)(&type)
int main()
{
    double x;
    printf("%d", my_sizeof(x));
    getchar();
    return 0;
}

Programme to find Nearest Vowel

This code is for finding nearest Vowel whatever Character you enter by your keyboard.

#include <stdio.h>
int main()
{
        int a[10]={65,69,73,79,85,97,101,105,111,117};  //Array of Vowel (a,e,i,o,u,A,E,I,O,U)
        char ch;
        int temp,temp1,i;
        printf ("enter character\n");
        scanf ("%c",&ch);
        temp=ch-a[0];
        for (i=0;i<10&&((ch-a[i])>=0);i++)
        {
                if( ch==a[i] )
                        {
                        printf ("nearest vowel is:  %c\n",a[i]);
                        return 0;
                        }
                if( temp>(ch-a[i]) )
                        {
                        temp1=a[i];
                        }

        }
        printf ("nearest vowel is %c\n",temp1);
        return 0;
}

Subtracting two numbers without using '-' operator

#include <stdio.h>

int add(int a,int b)

{

int x;

x=a^b;

while(a&b)

{

b=((a&b)<<1);

a=x;

x=a^b;

//b=(a^b);

}

return x;

}

int sub(int a, int b) // add a with b's 2's complement.

{

return (add(a, add(~b, 1)));

}

int main() {

int a, b, res;

a = 3, b = 1;

printf ("Enter two no\n");

scanf ("%d %d",&a,&b);

res = sub(a, b);

printf("%d\n", res);

printf ("After Sub. is  no  %d",res);

return 0;

} 

output: 

Enter two no

10

5

After Sub. no is 5

Add two numbers without using arithmetic operators

Add two numbers without using arithmetic operators:

Method 1:

#include<stdio.h>

int Add(int x, int y)
{
    // Iterate till there is no carry  
    while (y != 0)
    {
        // carry now contains common set bits of x and y
        int carry = x & y;  

        // Sum of bits of x and y where at least one of the bits is not set
        x = x ^ y; 

        // Carry is shifted by one so that adding it to x gives the required sum
        y = carry << 1;
    }
    return x;
}

int main()
{
    printf("%d", Add(15, 32));
    return 0;
}

Method 2:  (Using for Loop)

int sum(int num1, int num2)
{
    int total, temp, temptotal;  
    total = num1 ^ num2;    
  
    for(temp = num1 & num2; temp != 0;temp = temptotal & temp) 
      {      
      temptotal = total;    
      total = total ^ (temp = temp << 1);  
      }
  
   return total;
}