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 Need Help??
tye,
I expanded the code I came up with for combinations of a fixed size:
#!/usr/bin/perl use strict; use warnings; my \$iter = combo( 30..50 ); while ( my @combo = \$iter->() ) { print "@combo\n"; } sub combo { my @list = @_; return sub { () } if ! @_; my (@position, @stop, \$end_pos, \$done); my (\$by, \$next) = (0, 1); return sub { return () if \$done; if ( \$next ) { \$by++; return () if \$by > @list; @position = (0 .. \$by - 2, \$by - 2); @stop = @list - \$by .. \$#list; \$end_pos = \$#position; \$next = undef; } my \$cur = \$end_pos; { if ( ++\$position[ \$cur ] > \$stop[ \$cur ] ) { \$position[ --\$cur ]++; redo if \$position[ \$cur ] > \$stop[ \$cur ]; my \$new_pos = \$position[ \$cur ]; @position[ \$cur .. \$end_pos ] = \$new_pos .. \$new_pos + + \$by; } } if ( \$position[0] == \$stop[0] ) { \$position[0] == @list ? \$done = 1 : \$next = 1; } return @list[ @position ]; } }
I haven't analyzed its O factor or spent a lot of time with good benchmarks, but it does appear to be considerably faster for combinations of 30..50.

Cheers - L~R

In reply to Re^2: Finding all Combinations by Limbic~Region
in thread Finding all Combinations by narse

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