CODEWITHSUNDEEP
pythonpython-2.7bignum
DR.P
DR.P

Reputation: 43

script with big numbers take days

i am trying to run this script and its already run for 2 days. and still dont get answer. i tried long instead int. what am i supposed to do? what is the better way to work with big numbers like this? 

count=int(0)
sum1=int(1)
x=int(343543363925512)
y=int(98325112)
while x!=1:
    sum1=sum1+x
    if x%2!=0:
        x=x*3+1
    else:
         x=x/4

while y!=1:

    if y%2!=0:
        y=y*3+1
    else:
         y=y/4
    count=count+1

answer=int(sum1*count)
print answer

thank you very much.

Upvotes: 0

Views: 67

Answers (1)

chenxingwei
chenxingwei

Reputation: 261

as I know, the problem is the famous 3n+1 problem, which could be: when the number x % 2 == 0 then you should divide 2, but not 4.

count=int(0)
sum1=int(1)
x=int(343543363925512)
y=int(98325112)
while x!=1:
    sum1=sum1+x
    if x%2!=0:
        x=x*3+1
    else:
         x=x/2

while y!=1:

    if y%2!=0:
        y=y*3+1
    else:
         y=y/2
    count=count+1

answer=int(sum1*count)
print answer

The reason why your code have been running for two days is that your function go into endless loop.

Because you only exit the loop when x or y equals to 1, when x = 2, x % 2 == 0, then you will do x / 4 which get 0, x = 0 then runs forever.

Based on your code, you could do as

while x > 1:
    //do your things here

It is >, modified, same for y.

Upvotes: 3

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