# ETOOBUSY ðŸš€ minimal blogging for the impatient

# PWC114 - Higher Integer Set Bits

**TL;DR**

On with TASK #2 from the Perl Weekly Challenge #114. Enjoy!

# The challenge

You are given a positive integer

`$N`

.Write a script to find the next higher integer having the same number of 1 bits in binary representation as

`$N`

.

Example`Input: $N = 3 Output: 5 Binary representation of $N is 011. There are two 1 bits. So the next higher integer is 5 having the same the number of 1 bits i.e. 101. Input: $N = 12 Output: 17 Binary representation of $N is 1100. There are two 1 bits. So the next higher integer is 17 having the same number of 1 bits i.e. 10001.`

# The questions

Apart from assuming that the *input representation* will *necessarily*
be in base 10, I guess that no further clarifications are necessary.

# The solution

As I said in previous post PWC114 - Next Palindrome Number,
challenges can be addressed via *brute force* or with *aimed*
strategies.

Well, this time I opted for *brute force* ðŸ™„

I first take note of the number of bits in the input. Then I start counting from the successor, until I find a number with the same amount of bits. Soooo boring.

Hereâ€™s the complete program in Perl:

```
#!/usr/bin/env perl
use 5.024;
use warnings;
use experimental qw< postderef signatures >;
no warnings qw< experimental::postderef experimental::signatures >;
sub higher_integer_set_bits ($N) {
sub n_bits ($x) { sprintf('%b', $x) =~ tr/1/1/ };
my $initial = n_bits($N);
while ('necessary') {
++$N;
return $N if $initial == n_bits($N);
}
}
@ARGV = 3 unless @ARGV;
say higher_integer_set_bits($_) for @ARGV;
```

Hereâ€™s the correspondent program in (baby) Raku:

```
#!/usr/bin/env raku
use v6;
sub higher-integer-set-bits (Int $N is copy) {
sub n-bits ($x) { ($x.base(2) ~~ m:g/1/).elems };
my $initial = n-bits($N);
while True {
++$N;
return $N if $initial == n-bits($N);
}
}
sub MAIN (*@inputs is copy) {
@inputs.push(3) unless @inputs.elems;
higher-integer-set-bits($_).say for @inputs;
}
```

The old trick of counting stuff using the `tr`

operator seems to be gone
for good. Weâ€™re resorting to counting the matches, hoping itâ€™s not that
bad efficiency-wide (I mean, it will be a limited amount of bits
anyway).

Stay safe folks!

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