Speed

[Peter M. Brigham]

A followup on how to handle duplicate characters in the permuting algorithm. The following seems to work, not sure how it will scale. tString can contain any characters -- duplicates, digits, spaces, whatever.

function permute tString
   -- returns all the permutations in the string tString
   put (the length of tString) into N
   repeat with c = 1 to N
        put char c of tString into charAtLoc[c]
   end repeat
   subtract 1 from N
   put P2(N,49) into permList
   repeat with c = 1 to N+1
        replace c with charAtLoc[c] in permList
   end repeat
   return permList
end permute

function P2 N,B
   -- N is the depth to permute
   -- B is the ASCII value to start from
   -- so P2(1,49) returns 21 cr 12
   -- P2(2,53) returns 675 cr 765 cr 756 cr 576 cr 657 cr 567
   if N = 0 then return numToChar(B) & cr
   put P2(N - 1,B) into T
   add B to N
   repeat with i = B to N - 1
      put T into T2
      replace numToChar(i) with numToChar(N) in T2
      replace cr with numToChar(i) & cr in T2
      put T2 after R
   end repeat
   replace cr with numToChar(N) & cr in T
   return R & T
end P2

-- Peter

Peter M. Brigham
pmbrig at gmail.com
http://home.comcast.net/~pmbrig