Question

write a simple c program to reverse pairs of characters in a string. For exaple, "notified" becomes "edfitino". The reversal should be in this order in a simple easy to understand c program.

Answer 1

Hello the string reversal is done in 2 categories

1)when the string length is odd

-when it is odd,reversal is done from last index to 1st index and the 0th index is simply added to the last

2)when the string length is even

-when it is even the reversal is done in normal fashion itself

The input_string is the original string and ouput_string is the reversal string

//stdio is for standard input and output
#include <stdio.h>
//string is used for calculating length of the string
#include <string.h>
int main(int argc, char *argv[])
{
   char input_string[50]={'\0'},output_string[50]={'\0'};
   int i,length_of_string=0,j=0,count=0;
   //read the string
   printf("Enter the String which you want to reverse:");
   scanf("%s",input_string);
   //calculate the length of the string by using strlen() function
   length_of_string=strlen(input_string);
   for(i=length_of_string-1;i>=0;i--)
   {
       //when string length is even
       if(length_of_string%2==0)
       {
           //add last 2 charcters of the input to the first 2 characters and so on
           if((i+2)%2==0)
           {
               output_string[j++]=input_string[i];
               output_string[j++]=input_string[i+1];
           }
           else
           {
               continue;
           }
       }
       //when string length is odd
       else
       {
           //add first character at the last index
           if(i==0)
           {
               output_string[j]=input_string[i];
           }
           else if((i+2)%2==0)
           {
               continue;
           }
           //add last 2 charcters of the input to the first 2 characters and so on
           else
           {
               output_string[j++]=input_string[i];
               output_string[j++]=input_string[i+1];
           }
       }
   }
   printf("%s",output_string);
   return 0;
}

Thank you.....