Function to reverse string in C

Question

I wrote this function to reverse a string in C, but when switching characters in the string the program crashes. I have no idea what's causing it, so any help would be appreciated.

void reverse(char s[])
{
    char c;
    int i;
    int j;

    for (i = 0, j = (strlen(s) - 1); i < j; i++, j--)
    {
        c = s[i];
        s[i] = s[j]; //An error occurs here
        s[j] = c;
    }

    printf("%s", s);
}

main()
{
    reverse("Example");
}

You should create a new string, and return (or print) that one — Mathias711
– Mathias711, Commented Feb 27, 2014 at 13:21
@user3277234 Just so you know, in functions, arrays are actually pointers (that is, you have char *s, not char s[]). Changing a single character in a char pointer is undefined behavior. So please follow @Mathias711's advice and create a new string. — Diti
– Diti, Commented Feb 27, 2014 at 13:23
@Diti It is perfectly valid to modify characters, single or multiple. The real culprit is the string literal, s points to. — Olaf Dietsche
– Olaf Dietsche, Commented Feb 27, 2014 at 13:36

Community · Accepted Answer · 2017-05-23 10:26:11Z

3

read this for more information What is the difference between char s[] and char *s?

Another link https://stackoverflow.com/questions/22057622/whats-the-difference-structurally-between-char-and-char-string#22057685

this should fix it.

main()
{    
char array[] = "Example";
reverse(array); 
}

when you do reverse("Example") this is the same as

char *string = "Example";
reverse(string) //wont work

The links should clarify your doubts from here.

edited May 23, 2017 at 10:26

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answered Feb 27, 2014 at 13:23

tesseract

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Comments

Lee Duhem · Accepted Answer · 2014-02-27 13:25:38Z

1

"Example" is a string literal, which usually means you cannot change it.

Please try this:

char str[] = "Example";
reverse(str);

answered Feb 27, 2014 at 13:25

Lee Duhem

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Comments

user3065973 · Accepted Answer · 2014-02-27 13:25:17Z

0

This should work:

#include<string.h>

int main()
{
  char str[100], temp = 0;
  int i = 0, j = 0;

  printf("nEnter the string :");
  gets(str);

  i = 0;
  j = strlen(str)-1;

  while(i<j)
  {
    temp=str[i];
    str[i]=str[j];
    str[j]=temp;
    i++;
    j--;
  }

  printf("nReverse string is :%s",str);

  return(0);
}

answered Feb 27, 2014 at 13:25

user3065973

Comments

Leopold Joy · Accepted Answer · 2018-01-03 12:02:20Z

-1

You need to take character pointer as a parameter in your function:

Void reverse (char *ptr)
{
    // ...
}

And perform operation on pointer.

edited Jan 3, 2018 at 12:02

Leopold Joy

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answered Jan 3, 2018 at 9:46

user9146132

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