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# Vowel Strings
#
# Write a script to accept an integer 1 <= N <= 5 that would print all possible
# strings of size N formed by using only vowels (a, e, i, o, u).
#
# The string should follow the following rules:
#
# ‘a’ can only be followed by ‘e’ and ‘i’.
# ‘e’ can only be followed by ‘i’.
# ‘i’ can only be followed by ‘a’, ‘e’, ‘o’, and ‘u’.
# ‘o’ can only be followed by ‘a’ and ‘u’.
# ‘u’ can only be followed by ‘o’ and ‘e’.
#
# For example, if the given integer N = 2 then script should print the
# following strings:
#
# ae
# ai
# ei
# ia
# io
# iu
# ie
# oa
# ou
# uo
# ue
my %rules = 'a' => ['e', 'i'],
'e' => ['i'],
'i' => ['a', 'e', 'o', 'u'],
'o' => ['a', 'u'],
'u' => ['o', 'e'];
sub vowel-strings($n) {
if ($n == 1) {
return [['a'], ['e'], ['i'], ['o'], ['u']];
}
my @ret = [];
for vowel-strings($n - 1) -> @a {
for %rules{@a[*-1]}[*;*] -> $e {
@ret.push([|(@a), $e]);
}
}
return @ret;
}
sub MAIN($n) {
$_.say for vowel-strings($n).map({.join});
}
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