Five programming problems every Software Engineer should be able to solve in less than 1 hour

[Geoff Canyon]

Problem 5

Write a program that outputs all possibilities to put + or - or nothing
between the numbers 1, 2, ..., 9 (in this order) such that the result is
always 100. For example: 1 + 2 + 34 – 5 + 67 – 8 + 9 = 100.



function sumPermute S,T
   repeat
      put offset(",",line 1 of S) into F
      put F into fld 1
      wait 0 ticks
      if F = 0 then exit repeat
      put empty into newS
      repeat with i = 1 to 3
         put char i of "+- " into C
         repeat for each line L in S
            put C into char F of L
            put L & cr after newS
         end repeat
      end repeat
      put char 1 to -2 of newS into S
   end repeat
   repeat for each line L in S
      replace space with empty in L
      if value(L) = T then put L & cr after R
   end repeat
   return R
end sumPermute

Test Input
put sumPermute("1,2,3,4,5,6,7,8,9",100) into fld 1

Test Output
1+23-4+56+7+8+9
12+3-4+5+67+8+9
1+2+34-5+67-8+9
1+2+3-4+5+6+78+9
123-4-5-6-7+8-9
123+45-67+8-9
1+23-4+5+6+78-9
12-3-4+5-6+7+89
12+3+4+5-6-7+89
123-45-67+89
123+4-5+67-89