tring function

[muralidhary]

hello
can anyone write me a function for string reversal
without using string functions and without using a temporary
character array
to store the reversed string

[HarryW]

This code will only work in release mode if you're using VC++6. I don't know why, but VC++6 probably protects memory writes to make debugging easier or something. Anyway it works in release mode.

#include <iostream>

char *revstr(char *str)
{
	int length = strlen(str)-1;
	char *pstrstart = str; 
	char *pstrend = str + length;

	while((pstrend - pstrstart) > 0)
	{
		//swap characters
		*pstrstart = *pstrstart ^ *pstrend;
		*pstrend   = *pstrstart ^ *pstrend;
		*pstrstart = *pstrstart ^ *pstrend;
		pstrstart++;
		pstrend--;
	}

	return str;
}


int main()
{
	char *str = "abcde";
	std::cout << "revstr(\"abcde\") => " << revstr(str) << std::endl;
	
	return 0;
}

[HarryW]

Oops, just realised I had a string function in there (strlen).

Here's the alternative:

#include <iostream>

char *revstr(char *str)
{
	char *pstrstart = str; 
	char *pstrend = str;
	while(*(pstrend+1) != '\0')
		pstrend++;

	int length = pstrend - pstrstart-1;
	
	while((pstrend - pstrstart) > 0)
	{
		//swap characters
		*pstrstart = *pstrstart ^ *pstrend;
		*pstrend   = *pstrstart ^ *pstrend;
		*pstrstart = *pstrstart ^ *pstrend;
		pstrstart++;
		pstrend--;
	}

	return str;
}


int main()
{
	char *str = "abcde";
	std::cout << "revstr(\"abcde\") => " << revstr(str) << std::endl;
	
	return 0;
}

[muralidhary]

thank you HarryW

it is fine