如何匹配出现最长的子串？

lytton32

请各位指教一下如何做？

如有字串：
aaabaaaabaaaaabaaaaaaaabaaaaaaaaaaaabaabaaa

我想匹配出最长的那串a，如何做？我的预期是取到aaaaaaaaaaaa。谢谢了。

[ 本帖最后由 lytton32 于 2008-12-10 14:01 编辑 ]

MMMIX

文不对题嘛

churchmice

Do a global match with /g first
Extract from the result the longest match

1. 
   
2. #!/usr/bin/perl
   
3. use strict;
   
4. use warnings;
   
5. $_ = "aaabaaaabaaaaabaaaaaaaabaaaaaaaaaaaabaabaaa";
   
6. my @match = /(a+)/g;
   
7. my $max   = 0;
   
8. foreach (@match) {
   
9.     $max = $_ if ( length $_ > length $max );
   
10. }
    
11. print "Longest match is \[$max]\n";
    

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[ 本帖最后由 churchmice 于 2008-12-10 14:39 编辑 ]

churchmice

或者用这个
参考自mastering regular expression pattern

1. 
   
2. #!/usr/bin/perl
   
3. use strict;
   
4. use warnings;
   
5. $_ = "aaabaaaabaaaaabaaaaaaaabaaaaaaaaaaaabaabaaa";
   
6. my $pattern = qr/a+/;
   
7. my $longest = undef;
   
8. my $recordmatch = qr/(?{if ( not defined $longest or length $& > length $longest){$longest =$&;}})(?!)/;
   
9. m/$pattern$recordmatch/;
   
10. if (defined $longest){
    
11.         print "Longest match = \[$longest]\n";
    
12. }else {
    
13.         print "No match\n";
    
14. }
    

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lytton32

谢谢
收到了。