C++ Coding Logic - Various Ideas

[sankaran1984]

I want to write a method to determine if a given string is a palindrome. E.g. "Madam I'm Adam", or "A man, a plan, a canal, Panama".

The prototype for the function is:
bool is_palindrome(char const * str)

I have a simple logic to check for equality by moving forward & backward from extreme ends of the string.
But, i would like to know how many efficient ways to do this ? All ideas welcome from C++ gurus..

[Galik]

I'd be interested to see your algorithm for this. I would personally bung it into a std::string and use the STL algorithms to remove the spaces and punctuation and change the case before doing a reverse compare. But that's not necessarily very efficient.

[Bazzy]

You don't need <algorithm>, you can skip non-alphabetic characters while reading the string to compare the prefix and the suffix

[bluecoder]

What code have you written to implement this palindrome.

[stravant]

Fun trick to use, lowercase characters by and'ing the 6th bit, (char & 0x20) == lowercase(char), provided you know they are alpha characters.

[Bazzy]

you can use <cctype> functions instead...

[jmc]

Fun trick to use, lowercase characters by and'ing the 6th bit, (char & 0x20) == lowercase(char), provided you know they are alpha characters.

Even funnier is that this ain't gonna work ;)
You might mean bitwise OR instead of bitwise AND. You would not get a lot of a bitwise AND in this case.

[stravant]

Yea, sorry, mixed that up.
char & ~0x20 == uppercase
char | 0x20 == lowercase