1.1 --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
     1.2 +++ b/palindrome/is_palindrome.cpp	Tue May 05 12:02:16 2015 -0500
     1.3 @@ -0,0 +1,34 @@
     1.4 +#include <cstring>
     1.5 +#include <cctype>
     1.6 +#include <iostream>
     1.7 +#include <string>
     1.8 +
     1.9 +bool is_palindrome( const char *s ) {
    1.10 +    const char * first = s;
    1.11 +    const char * last = s + strlen(s) - 1;
    1.12 +    while ( first < last ) {
    1.13 +        while ( ! isalpha( *first ) && *first != 0 )
    1.14 +            first++;
    1.15 +        while ( ! isalpha( *last ) && last >= s )
    1.16 +            last--;
    1.17 +        if ( toupper( *first ) != toupper( *last ) ) {
    1.18 +            return false;
    1.19 +            }
    1.20 +        first++;
    1.21 +        last--;
    1.22 +        }
    1.23 +    return true;
    1.24 +    }
    1.25 +
    1.26 +bool is_palindrome( std::string s ) {
    1.27 +    return is_palindrome( s.c_str() );
    1.28 +    }
    1.29 +
    1.30 +int main ( int argc, char **argv ) {
    1.31 +    for ( int i = 1; i < argc; ++i ) {
    1.32 +        std::string s(argv[1]);
    1.33 +        std::cout << is_palindrome( s ) << std::endl;
    1.34 +        }
    1.35 +
    1.36 +    return 0;
    1.37 +    }

     2.1 --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
     2.2 +++ b/palindrome/is_palindrome.pl	Tue May 05 12:02:16 2015 -0500
     2.3 @@ -0,0 +1,31 @@
     2.4 +use strict;
     2.5 +use warnings;
     2.6 +
     2.7 +# This implements the same algorithm as the C++ version, but it has to first
     2.8 +# split the string into an array, and therefore uses O(N) extra space.
     2.9 +
    2.10 +sub is_palindrome {
    2.11 +    my $s = shift;
    2.12 +    my @chars = split( //, $s );
    2.13 +    my $first = 0;
    2.14 +    my $last = scalar( @chars ) - 1;
    2.15 +    while ( $first < $last ) {
    2.16 +        while ( ( $chars[$first] !~ /^[a-zA-Z]$/  ) and ( $first < scalar( @chars ) ) ) {
    2.17 +            $first++;
    2.18 +        }
    2.19 +        while ( ( $chars[$last] !~ /^[a-zA-Z]$/  ) and ( $last > 0 ) ) {
    2.20 +            $last--;
    2.21 +        }
    2.22 +
    2.23 +        if ( lc($chars[$first]) ne lc($chars[$last]) ) {
    2.24 +            return 0;
    2.25 +        }
    2.26 +        $first++;
    2.27 +        $last--;
    2.28 +    }
    2.29 +    return 1;
    2.30 +}
    2.31 +
    2.32 +for ( my $i = 0; $i < scalar( @ARGV ) ; $i++ ) {
    2.33 +    print is_palindrome( $ARGV[$i] ) . "\n";
    2.34 +}