RosettaCodeData/Task/Find-the-missing-permutation/Sidef/find-the-missing-permutation.sidef

func check_perm(arr) {
    var hash = Hash()
    hash.set_keys(arr...)
    arr.each { |s|
        {
            var t = (s.substr(1) + s.substr(0, 1))
            hash.has_key(t) || return t
        } * s.len
    }
}

var perms = %w(ABCD CABD ACDB DACB BCDA ACBD ADCB CDAB DABC BCAD CADB CDBA
               CBAD ABDC ADBC BDCA DCBA BACD BADC BDAC CBDA DBCA DCAB)

say check_perm(perms)