Thread: reverse a string

Hi Guys, Happy New Year to all of you!! I wrote the following code to reverse a string input from user. I'm wondering if there is a better way to go about this. Any suggestions please?

Code:

int main() {
 char string[256];
 int len;

 printf("Enter a string:\n");
 fgets(string, 256-1, stdin);
 len = (strlen(string) - 1);
 printf("You entered %s \nlength %d:\n", string, len);

 printf("Reverse string:");
 for(; len >= 0; len--)
        printf("%c",string[len]);

 printf("\n");
 exit(0);
}

Originally Posted by Prelude

You need to include these guys:

Code:

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

Actually I did include the above in read code. Just skipped these to save some space

>fgets(string, 256-1, stdin);
There's no need to subtract one from the size. fgets does the right thing.

Ok, good to know that!

>I'm wondering if there is a better way to go about this.
There's nothing wrong with your solution. What more do you need? In this case, "better" is defined by the requirements of your program.

I am writing this just for educational/practise purpse. Thought maybe some improvements can be made to the way a string can be reversed.

>exit(0);
Most people will use return from main rather than exit.

Thank you for this input. I'll keep this in mind!

Thank you again for your reply!!

I would suggest that you reverse the string in place and then print it with "%s" format specifier. That way you save multiple calls to printf.

Originally Posted by pankaj401

I would suggest that you reverse the string in place and then print it with "%s" format specifier. That way you save multiple calls to printf.

Thank you so much for your suggestion. I have made some changes to my code taking your suggestion:

Code:

//This is a small program to reverse the string provided by user
#include<stdio.h>
#include<string.h>

int main() {
 char string[256], revstr[256];
 int len, i;

 printf("Enter a string:\n");
 fgets(string, 256-1, stdin);
 len = (strlen(string) - 1);
 printf("You entered %s \nlength %d:\n", string, len);
 i = len;
 printf("Reverse string:");
 for(; len >= 0; len--)
        revstr[i-len] = string[len];

 revstr[i+1] = '\0';
 printf("Reversed string is: %s\n", revstr);
 exit(0);
}

You could reverse the string by swapping characters up to half way through the string with the corresponding characters on the other half of the string. Just a different way of doing it:

Code:

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

void Reverse(char* string)
{
	int len = strlen(string)-1;
	int mid = len / 2;
	int pos;
	char tmp;

	for(pos=0; pos<mid; pos++)
	{
 		tmp = string[pos];
		string[pos]	= string[len-pos];
		string[len-pos] = tmp;
	}		
}

int main()
{
	char string[256];
	fgets(string, 256, stdin);
	string[strlen(string)-1]='\0';
	printf("Normal: %s\n", string);
	Reverse(string);
	printf("Reversed: %s\n", string);
	Reverse(string);
	printf("Back again: %s\n", string);
	getchar();
	return 0;
}