Reverse string

C programming code

/* String reverse in c*/

#include <stdio.h>
#include <string.h>
 
int main()
{
   char arr[100];
 
   printf("Enter a string to reverse\n");
   gets(arr);
 
   strrev(arr);
 
   printf("Reverse of entered string is \n%s\n",arr);
 
   return 0;
}

Download Reverse string program.

Output of program:

/* Second method */

C program to reverse a string using pointers

: Now we will invert string using pointers or without using library function strrev.

#include<stdio.h>
 
int string_length(char*);
void reverse(char*);
 
main() 
{
   char string[100];
 
   printf("Enter a string\n");
   gets(string);
 
   reverse(string);
 
   printf("Reverse of entered string is \"%s\".\n", string);
 
   return 0;
}
 
void reverse(char *string) 
{
   int length, c;
   char *begin, *end, temp;
 
   length = string_length(string);
 
   begin = string;
   end = string;
 
   for ( c = 0 ; c < ( length - 1 ) ; c++ )
      end++;
 
   for ( c = 0 ; c < length/2 ; c++ ) 
   {        
      temp = *end;
      *end = *begin;
      *begin = temp;
 
      begin++;
      end--;
   }
}
 
int string_length(char *pointer)
{
   int c = 0;
 
   while( *(pointer+c) != '\0' )
      c++;
 
   return c;
}

C program to reverse a string using recursion

#include <stdio.h>
#include <string.h>
 
void reverse(char*, int, int);
 
int main()
{
   char a[100];
 
   gets(a);
 
   reverse(a, 0, strlen(a)-1);
 
   printf("%s\n",a);
 
   return 0;
}
 
void reverse(char *x, int begin, int end)
{
   char c;
 
   if (begin >= end)
      return;
 
   c          = *(x+begin);
   *(x+begin) = *(x+end);
   *(x+end)   = c;
 
   reverse(x, ++begin, --end);
}

In recursion method we swap characters at the begin and at the end and then move towards the middle of the string. This method is inefficient due to repeated function calls but useful in practicing recursion.