Efficient way to reverse the string inplace in c++??

[Super Hornet]

Expecting favourable reply.

[toxcct]

Super Hornet wrote:

Expecting favourable reply

Explecting explicit and clear question, with code snippets and all that i need to understand the point with ambiguity...

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[Super Hornet]

//function that retuens the reverse of passed string
char *ReverseString(char *pszString)
{
if (pszString) //check for valid pointer
{
int ilength = strlen(pszString) + 1; //length of string including '\0'

	for (int iIndex = ilength; iIndex > 0; iIndex--)
	{
		pszString\[i\] = pszString\[i-1\];  
	}

	pszString\[0\] = '\\0';
  
	return &pszString\[ilength\];
}
else
{
	return NULL;
}

}

//program to reverse the string inplace

int main()
{
char szString[] = "hello world";

//prints the string before calling ReverseString method
cout << "String before reversing " << szString;

szString = ReverseString(szStirng); //returns the reverse of a string

//prints the string after calling ReverseString method
cout << "\\n String after reversing " << szString;

}

Is the above code correct???

[toxcct]

hum... bad habits lead to bad code... you're using C++, so use it entierely. first of all, abandon the C-style strings (char*), it's just a pain to use when you can make use of the string class. here is another solution:

std::string ReverseString(const std::string& str) {
std::string strTmp;

std::string::const\_reverse\_iterator iter;
for (iter = str.rbegin(); iter != rend(); --iter) {
    strTmp += \*iter;
}

return strTmp;

}

you could also use the swap technic:

std::string ReverseString(const std::string& str) {
std::string strTmp = str;

size\_t len = strTmp.length();
for (size\_t i = 0; iter < len/2; i++) {
    strTmp\[i\] = str\[len-i\];
    strTmp\[len-i\] = str\[i\];
}

return strTmp;

}

or even more powerful, using the STL algorithms (thanks jijo raj):

std::string ReverseString(const std::string& str) {
return std::reverse(str.begin(), str.end());
}

now in your main, just call it:

int main(int argc, char* argv[]) {
std::string s = "Hello World";

std::cout << "Before reversing : " << s <<endl;
std::cout << "After reversing  : " << ReverseString(s) << endl;

}

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modified on Wednesday, August 6, 2008 6:00 AM

[Jijo Raj]

You can further optimize it by using std::reverse() algorithm...

// Reverse it by using the Reverse alogrithm.
string Str = _T("Hello");
reverse( Str.begin(), Str.end());

Regards, Jijo.

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[Naveen]

Dosen't string have a reserve() function? :confused:

nave [OpenedFileFinder]

[toxcct]

Naveen wrote:

Dosen't string have a reserve() function?

reserve() ? what for ?

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[toxcct]

damn it, i was sure such a functor was existing somewhere, but i couldn't put a hand on it though. thanks for the notice.

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[Naveen]

ops My bad. sorry I miss read the reserve as reverse.

nave [OpenedFileFinder]

[Jijo Raj]

:laugh: Regards, Jijo.

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[Super Hornet]

Thanks a-lot toxcct

[David Crow]

Super Hornet wrote:

Is the above code correct???

That all depends on what you were trying to accomplish. The use of cout appears to be the only thing C++ that I see.

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