Perl weekly challenge 114, Task #2

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Perl weekly chanllege 114, Task #2 Higher Integer Set Bits

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.

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my method bits-number(UInt:D $n: --> UInt:D) { $n.base(2).comb.grep(1).elems }

my method has-bits(UInt:D $n: UInt:D $bits --> Bool:D) { $n.&bits-number == $bits }

my $N = $*IN.slurp.UInt;

put ($N^..*).grep(*.&has-bits($N.&bits-number))[0];