Reverse String C++

HelloWorld · #1 (**permalink**) 03-28-2008, 02:07 AM

Why doesn't the code below works..? It throws some weird error from VS..

Code:

#include <iostream>
#include <string>

using namespace std;

void ReverseString (char *String)
{
	char *Begin = String;
	char *End = String + strlen(String) - 1;
	char TempChar = '\0';

	while (Begin < End)
	{
		Begin++;
		End--;
	}
}

int main()
{
	ReverseString("hello");
	return 0;
}

any ideas..?

MrPickle · #2 (**permalink**) 03-28-2008, 02:18 AM

Maybe if you tell us the errors we can help you more (:

ccoonen · #3 (**permalink**) 03-28-2008, 02:33 PM

Seems like their is some circular logic going on here... incrementing while decrementing - or is String a reserved word? or are you supposed to reference String as a pointer in the FUnction too? (like *String instead of String)?

Here's a recursive fuinction reversiing a string in C++

Code:

Recursive Reverse String Algorithm

The Shortest function to reverse a string.

Written by: Sanchit Karve
            born2c0de AT hotmail.com
[born2c0de]
*/

#include <iostream>

using namespace std;

void ret_str(char* s)
{
    if(*s != '\0')
         ret_str(s+1);

    cout<<*(s);
}

int main()
{
   ret_str("born2c0de");
   return 0;
}

HelloWorld · #4 (**permalink**) 03-28-2008, 05:21 PM

much nicer code, but I hate recursive though lol... oh well, looks much nicer

MrPickle · #5 (**permalink**) 03-29-2008, 06:06 AM

You could use a for loop of the string's length and do something like

Code:

ReversedString[i] = String[StringLength-i];

Bench · #6 (**permalink**) 03-30-2008, 04:25 PM

the problem is that "hello" is a string literal, and cannot be modified, so its undefined behaviour and VS is right to throw up an error.

change your main to something like this

Code:

int main()
{
    //"hello" is now copied into a char[]
    char str[] = "hello";
    ReverseString( str ); 
}

This is one of the reasons why char* is often considered bad, because there's no protection for programmers accidentally doing this sort of thing. in C++, if you always use the string type, you can't go wrong.

edit you're also missing the code which actually swaps the characters in your string - all you're doing is iterating 2 pointers which don't actually modify the char array

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