Stuck on Project Euler # 13

Question

Please help me understand why my Python code to solve the 13th Project Euler problem is incorrect. I believe that I understand the task correctly and I think my code is correct, but it is obviously not.

number = '5000 digit number - see in the problem decription at the provided link'
list1 = [number[i:i+100] for i in range(0, len(number), 100)]
temp = []
for i in range(0, len(list1)):
    y = int(list1[i])
    temp.append(y)
print sum(temp)

Asked By: Taras_G

||

Source

Answer 1

First, the numbers are 50 digits long, not 100. Change this:

list1 = [number[i:i+100] for i in range(0,len(number),100)]

To this:

list1 = [number[i:i+50] for i in range(0,len(number),50)]

Second, you’re printing the entire sum, rather than just the first ten digits. Try:

print str(sum(temp))[:10]

Answered By: Kevin

Answer 2

Much simpler:

s = 'copied and pasted from the page'

result = sum(map(int, s.splitlines()))[:10]

Answered By: Adam Smith

Answer 3

Only the 11 first digits need to be summed,

somme11=sum(int(number2[i:i+11]) for i in range(100))
print(somme11)
print( 'the ten first digits are' , somme11//1000)

Because the carry can’t exceed 99.

4893024188690
the ten first digits are 4893024188

Answered By: B. M.

Answer 4

An alternative is to load the numbers into a file and then just add them up, unless I too have completely misunderstood the question.

with open("sum.nums","r") as f:
    data = f.readlines()
total = 0
for i in data:
    total += int(i)
print "1st 10 digits ", str(total)[:10], "of total", total

1st 10 digits 5537376230 of total 5537376230390876637302048746832985971773659831892672

Answered By: Rolf of Saxony

Answer 5

It’s pretty simple

def e13():
    f=open("100x50digits.txt")
    summ=0
    for line in f:
        summ+=int(line[:11])
    print(int(summ/1000))
    f.close()
e13()

Answered By: Mike Zubko

Answer 6

number = '''The 100 lines of 50 characters'''

numbers = number.splitlines()          #Devide the string into a list of strings.
numbers = [int(i) for i in numbers]    #Convert all elements into integers.
totalSum = str(sum(numbers))           #Add everything and convert to a string.
print(totalSum[:10])                   #Print the first 10 digits of the result.

The correct answer is 5537376230, checked with P.E.

The real challenge here is to deal with the really long string

Answered By: Sigmatest

Answer 7

Use StringIO to take number as a input string and iterate trough elements by converting each one to a integer value

from io import StringIO

number = StringIO(""" # Paste one-hundred 50 numbers """) 

print(str(sum(map(lambda x: int(x), number)))[:10])
>>> '5537376230'

Answered By: user11717481

Stuck on Project Euler # 13

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