Problem Description

If the numbers 1 to 5 are written out in words: one, two, three, four, five, then there are 3 + 3 + 5 + 4 + 4 = 19 letters used in total.

If all the numbers from 1 to 1000 (one thousand) inclusive were written out in words, how many letters would be used?

NOTE: Do not count spaces or hyphens. For example, 342 (three hundred and forty-two) contains 23 letters and 115 (one hundred and fifteen) contains 20 letters. The use of “and” when writing out numbers is in compliance with British usage.

Analysis

Converted the integers from 1 to 999 to the written equivalent, removed spaces and hyphens, added the character count for each one, including “onethousand”.

Solution

Runs < 1 second in Perl.

@D{0 .. 20, 30,40,50,60,70,80,90} = qw|
 zero one two three four five six seven eight nine ten
 eleven twelve thirteen fourteen fifteen sixteen seventeen eighteen nineteen
 twenty thirty forty fifty sixty seventy eighty ninety|;
 
for $i (1..999) {
  $x= num2en($i); $x=~s/[s-]//g;
  $l+= length($x);
}
print "Answer to PE17 = ",$l+length('onethousand');
 
sub num2en {
  my($x) = $_[0];
  return $D{$x} if defined $D{$x};
  return  $D{$1 . '0'} . '-' . $D{$2} if( $x =~ m/^(.)(.)$/ );
  if ( $x =~ m/^(.)(..)$/ ) {
      my($h, $rest) = ("$D{$1} hundred", $2);
      return $h if $rest eq '00';
      return "$h and " . num2en($rest);
  }
}

Comments