CODEWITHSUNDEEP
python
user161440
user161440

Reputation: 101

Where was I wrong in my reasoning?

I'm an absolute beginner in programming in Python and this is my first program in Project Euler (problem 1).

Problem 1 in Project Euler asks:

If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.

Find the sum of all the multiples of 3 or 5 below 1000.

I feel like my reasoning is wrong somewhere, but I can't see where or why? I get 266333.

i=0
s=0
j=0
r=0

while i<1000:
  s=s+i
  i=i+3

while j<1000:
  r=r+j
  j=j+5
print("sum=",s+r)

Upvotes: 0

Views: 83

Answers (2)

Weafs.py
Weafs.py

Reputation: 22998

The question is:

Find the sum of all multiples of 3 or 5 below 1000.

All you need to do here is loop through the numbers below 1000, if the number is divisible by 3(i % 3 == 0) or 5(i % 5 == 0), append it to a list multiples and print the sum of all the elements of multiples(sum(multiples)).

multiples = []

for i in range(1000):
    if i % 3 == 0 or i % 5 == 0:
        multiples.append(i)

print sum(multiples)
# 233168

More simplified code:

print sum([i for i in range(1000) if i % 3 == 0 or i % 5 == 0])
# 233168

Upvotes: 2

Satanicpuppy
Satanicpuppy

Reputation: 1587

You're adding some numbers twice. 15, for example, is a multiple of 3 and 5, but you shouldn't add it twice.

I'd do something simpler using modulo, and only one loop.

Example (haven't tested):

x=0
y=0

while x<1000
   if (x%5==0 or x%3==0):
      y=y+x
   x+=1

print("Sum equals ",y)

Upvotes: 0

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