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Re: Find last position of an element in array

by dbuckhal (Chaplain)
on Mar 29, 2022 at 17:38 UTC ( [id://11142504]=note: print w/replies, xml ) Need Help??


in reply to Find last position of an element in array

skipping past the sigil or brace mismatch, here is my five minute contribution...

perl -le '
  my @arr = (1,1,1,2,2,2,2,2,3,3,3,4,4,4,4,4,4,5,5,6);
  print (@arr - index((reverse(@arr)), 4));
'
__output__
17

[download]

Replies are listed 'Best First'.
Re^2: Find last position of an element in array
by kcott (Archbishop) on Mar 29, 2022 at 21:49 UTC

    G'day dbuckhal,

    17 = off-by-one error. Fix: use $#arr instead of @arr. 

    $ perl -le '
  my @arr = (1,1,1,2,2,2,2,2,3,3,3,4,4,4,4,4,4,5,5,6);
  print ($#arr - index((reverse(@arr)), 4));
  print "@arr[16, 17]";
'
16
4 5

    [download]

    — Ken

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[d/l]
[select]
Re^2: Find last position of an element in array
by hippo (Bishop) on Mar 30, 2022 at 09:49 UTC

    You can avoid the maths with rindex:

    $ perl -le '
my @arr = (1,1,1,2,2,2,2,2,3,3,3,4,4,4,4,4,4,5,5,6);
print rindex( join (q{}, @arr), 4 );  
'
16

    [download]

    🦛

[reply]
[d/l]

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