| 03 January 2024 | Challenge 250 |
Alphanumeric Moduli
Task 1: Smallest Index
Submitted by: Mohammad S Anwar
You are given an array of integers, @ints.
Write a script to find the smallest index i such that i mod 10 == $ints[i] otherwise return -1.
Example 1
Input: @ints = (0, 1, 2)
Output: 0
i=0: 0 mod 10 = 0 == $ints[0].
i=1: 1 mod 10 = 1 == $ints[1].
i=2: 2 mod 10 = 2 == $ints[2].
All indices have i mod 10 == $ints[i], so we return the smallest index 0.
Example 2
Input: @ints = (4, 3, 2, 1)
Output: 2
i=0: 0 mod 10 = 0 != $ints[0].
i=1: 1 mod 10 = 1 != $ints[1].
i=2: 2 mod 10 = 2 == $ints[2].
i=3: 3 mod 10 = 3 != $ints[3].
2 is the only index which has i mod 10 == $ints[i].
Example 3
Input: @ints = [1, 2, 3, 4, 5, 6, 7, 8, 9, 0]
Output: -1
Explanation: No index satisfies i mod 10 == $ints[i].
Solution
Whenever we loop over an array and need both the index and the value, each comes handy.
Here we return the first index that equals the value modulo a given base or -1 if none is found.
sub smallest_index {
my $base = shift;
while (my ($i, $n) = each @_) {
return $i if $n == $i % $base;
}
-1;
}
See the full solution.
Task 2: Alphanumeric String Value
Submitted by: Mohammad S Anwar
You are given an array of alphanumeric strings.
Write a script to return the maximum value of alphanumeric string in the given array.
The value of alphanumeric string can be defined as
a) The numeric representation of the string in base 10 if it is made up of digits only.
b) otherwise the length of the string
Example 1
Input: @alphanumstr = ("perl", "2", "000", "python", "r4ku")
Output: 6
"perl" consists of letters only so the value is 4.
"2" is digits only so the value is 2.
"000" is digits only so the value is 0.
"python" consits of letters so the value is 6.
"r4ku" consists of letters and digits so the value is 4.
Example 2
Input: @alphanumstr = ("001", "1", "000", "0001")
Output: 1
Solution
Using a simple regex we can check if a given string consists of digits only. If it does, we use its numeric value and otherwise the string’s length. max provides the requested maximum value.
use List::Util 'max';
sub max_val {
max map /^\d+$/ ? 0 + $_ : length, @_;
}
See the full solution.
If you have a question about this post or if you like to comment on it, feel free to open an issue in my github repository.