A combination of coins to give as close or exact as possible to 200 grams

[izuzetan]

Where did I go wrong? The goal is to find the number and combination of coins weighing 5.78 grams, 5.05 grams and 4.2 grams to give as close as possible or exactly 200 grams. It is QBASIC. Is there such a thing on the internet?

din = 0
pet = 0
dva = 0


aktuelno = 250



for a = 0 to 48
pet = din

for b = 0 to 41 - a
pet = dva + din


for c = 1 to 36 - b - a

pet = pet + 5.78
tekuce = ABS(200 - pet)

if tekuce < aktuelno
   aktuelno = tekuce
   pamtimdin = a
   pamtimdva = b
   pamtimpet = c
end if

next c
dva = dva + 5.05

next b
dinar = dinar + 4.2

next a


print aktuelno

print "pet: " ; pamtimpet
print "dva: " ; pamtimdva
print "din: " ; pamtimdin

 

[WhiteCube]

All 3 loops can go from 0 to 50, because you're using a brute force method. Extra iterations won't hurt, and it keeps things simple.

aktuelno = 201
for a = 0 to 50
  for b = 0 to 50
    for c = 0 to 50
      pet = 4.2*a + 5.05*b + 5.78*c
      tekuce = ABS(200 - pet)
      if tekuce < aktuelno
        aktuelno = tekuce
        pamtimdin = a
        pamtimdva = b
        pamtimpet = c
      end if
    next c
  next b
next a
print aktuelno
print "pet: " ; pamtimpet
print "dva: " ; pamtimdva
print "din: " ; pamtimdin

The inner loop can be removed, c can be calculated directly from a and b. It's a bit messy.

for a = 0 to FLOOR(200/4.2)
  for b = 0 to FLOOR((200 - 4.2*a)/5.05)
    c = (200 - 4.2*a - 5.05*b)/5.78
    c = FLOOR(c + 0.5)
    ...