问题：编写一个函数来解析给定的字符串以获得以下给定的规则&生成最终解析的字符串作为输出

写一个接受字符串作为输入的函数,字符串长度将在[0..2000000000]之间

string should be made from only ‘A’,’B’ & ‘C’ characters like ‘AAA’,’ABCABC’,’AAAABBBBABAAACCCA’

转型规则：

1)’AB’ – > ‘AA’
2)’AC’ – > ‘AA’
3)’AA’ – > ‘一个’
4)’CC’ – > ‘C’
5)’BC’ – > ‘BB’
6)’BB’ – > ‘B’

每次在给定字符串上随机应用以上6条规则,并将最终转换后的字符串作为输出

例如,对Function的输入是：’ABCAAB’字符串

ABCAAB – > AACAAB [AB = AA]
AACAAB – > ACAAB [AA = A]
ACAAB – > AAAAB [AC = AA]
AAAAB – > AAAB [AA = A]
AAAB – > AAB [AA = A]
AAB – > AB [AA = A]
AB – > AA [AB = AA]
AA – > A [AA = A]

最终结果：’A’

因为我们现在无法对字符串应用任何其他规则.

我的答案就像(伪代码)：

sub myFunc {
my $str = @_;
flag = 1
while(flag ==1) {
    if ($str =~ /AB/){
    $str =~ s/AB/AA/;
    next;
    }
    elsif($str =~ /AC/){
    $str =~ s/AC/AA/;
    next;
    }
    elsif($str =~ /AA/){
    $str =~ s/AA/A/;
    next;
    }
    elsif($str =~ /CC/){ 
    $str =~ s/CC/C/;
    next;
    }
    elsif($str =~ /BC/){ 
    $str =~ s/BC/BB/;
    next;
    }
    elsif($str =~ /BB/){ 
    $str =~ s/BB/B/;
    next;
    }
    else
    {
        flag = 0
    }
} //while
 return $str;
} //func

有人可以建议更好的算法&处理上述问题？