To me, the first good questions would be: 1. What language(s) does this function have to be callable from? 2. Can I write it in any language? Rather than “Is

To me, the first good questions would be: 1. What language(s) does this function have to be callable from? 2. Can I write it in any language? Rather than “Is this client side or server side JavaScript?” Considering that I have no idea how to use a regex for this, it was very strange to read that the interviewer expected _many_ people would use a regex. Made me feel like I missed a year of school or something. For efficiency, only half of the string needs to be tested, not the whole thing. (Edit: I realized later that the posted JS does this too. It was not obvious at first because "end" is also changing.) Since I never actually do these things, I thought it might be fun to code one. First I wrote the simple function, pal1(). Then I wondered if Python had a built-in string reverse function, so looked that up with Google and found that it didn't. It has a klunky reversed() iterator, but there was the obtuse s[::-1] post on Stack Overflow that runs fast, so added that as an alternative. And I had to lookup the __name__ line, because I forgot the syntax of that, even though I've been writing Python (HashBackup backup program) for 7 years! import sys # the straightforward way, char-by-char compare def pal1(s): slen = len(s) slenm1 = slen - 1 for i in xrange(slen/2): if s[i] != s[slenm1-i]: return False return True # s[:-5] === "the last 5 (or fewer) characters of s" # s[::] === s === s[start:end:incr], where start=0, end=len(s), and incr=1 # s[::-1] === reverse(s) == s[end:start:incr], where start=0, end=len(s), and incr=-1 def pal2(s): return s == s[::-1] # select which palindrome function to use pal = pal1 # test with: # 1. null string # 2. single char (odd length) # 3. double char string (even length) if __name__ == '__main__': if len(sys.argv) != 2: print 'usage: pal <string>' else: s = sys.argv[1] if pal(s): print 'yep' else: print 'nope'