Perl Weekly Challenge: Week 85
Challenge 1:
Triplet Sum
You are given an array of real numbers greater than zero.
Write a script to find if there exists a triplet
(a,b,c)such that1 < a+b+c < 2. Print 1 if you succeed otherwise 0.
Example 1:
Input: @R = (1.2, 0.4, 0.1, 2.5)
Output: 1 as 1 < 1.2 + 0.4 + 0.1 < 2
Example 2:
Input: @R = (0.2, 1.5, 0.9, 1.1)
Output: 0
Example 3:
Input: @R = (0.5, 1.1, 0.3, 0.7)
Output: 1 as 1 < 0.5 + 1.1 + 0.3 < 2
In Raku, we can do this as a one-liner.
say @*ARGS.combinations(3).grep({ ([+] @_) ~~ 1.0 .. 2.0 }).elems ?? 1 !! 0;
Perl is more verbose, lacking as it does some of Rakus' features. combinations() is my
tried and trusted Perl workalike I used most recently in PWC 83.
my $results = 0;
for my $combo (combinations(\@ARGV, 3)) {
my $total = 0;
for my $elem (@{$combo}) {
$total += $elem;
}
if ($total > 1.0 && $total < 2.0) {
$results++;
}
}
say $results ? 1 : 0;
Challenge 2:
Power of Two Integers
You are given a positive integer
$N.Write a script to find if it can be expressed as
a ** bwherea > 0andb > 1. Print 1 if you succeed otherwise 0.
Example 1:
Input: 8
Output: 1 as 8 = 2 ** 3
Example 2:
Input: 15
Output: 0
Example 3:
Input: 125
Output: 1 as 125 = 5 ** 3
As I sat down to solve this, I had a nagging suspicion that I had done something like it before. Sure enough,
this is extremely similar to the "Power Integers" challenge in PWC 66. I reused the isPower() function I had developed for that challenge. The only
change I needed to make to it was to disallow (1,1) as our spec clearly states that b > 1. Once I had that function
working properly, the solution to this challenge became a one liner.
say scalar isPower(shift) ? 1 : 0;
Note that isPower() returns all powers of two integers but for this problem we only need to know if there was atleast 1 and
we don't even have to print out what it was.
This is the Raku version wrapped up in sub MAIN() though that isn't strictly necessary.
sub MAIN(Int $N) {
say isPower($N).elems ?? 1 !! 0;
}