Jussi Piitulainen wrote:
Ian writes:
If you want to or must do it recursively.
(Shown in pseudo code to make the logic clearer)
def isPalindrome(pal)
''' test pal (a list) is a palindrome '''
if length of pal = 1
return True # all one letter strings are palindromes.
if first equals last
# pal could be a palindrome
# so test inner part
p = pal with first and last removed
return isPalendrome(p) # and true - implied
else
return False # it can't be
def palindromep(s):
return ( s == "" or
( s[0] == s[-1] and
palindromep(s[1:-1]) ) )
Of course, the simpler way is to use the definition of a Palindrome
as the same backwards and forwards.
def isPalindrome(pal)
return pal == pal.reverse
Agreed. But is there any nicer way to spell .reverse than [::-1] in
Python? There is .swapcase() but no .reverse(), right?
There can't be a .reverse() method on string, because it's immutable.
You could use
"".join(reversed(pal))
but I'd prefer pal[::-1] as I said earlier.
DaveA
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