Reverse string

This program reverses a string entered by the user. For example if a user enters a string "reverse me" then on reversing the string will be "em esrever". We show you three different methods to reverse string the first one uses strrev library function of string.h header file and in second we make our own function to reverse string using pointers, reverse string using recursion and Reverse words in string. If you are using first method then you must include string.h in your program.

C programming code

/* String reverse in c*/

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

/* 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);
 
main()
{
   char a[100];
 
   gets(a);
 
   reverse(a, 0, strlen(a)-1);
 
   printf("%s\n",a);
 
   return 0;
}
 
void reverse(char *x, int beg, int end)
{
   char a, b, c;
 
   if ( beg >= end )
      return;   
 
   c = *(x+beg);
   *(x+beg) = *(x+end);
   *(x+end) = c;
 
   reverse(x, ++beg, --end);
}

Reverse string program executable. Output of program: