Python Project Euler - 1 , 2 , 3 , 4

like 'lets play' but with more code
Slightly more advanced python doing some number problems from ProjectEuler. List comprehensions and generator expressions. Generators.

1) Multiples of 3 and 5
2) Even Fibonacci numbers
3) Largest prime factor
4) Largest palindrome product

[Philgob]

“Obviously I’m not doing it right... But I feel like it’s right”

Programming in a nutshell

[counterretort]

Solving the problem first and then watching your videos is a great way of learning to write better code. I'm enjoying myself immensely, thank you very much!

[andrewlee]

For the 3rd problem, when you factored 21, it only output 3 as it's factors, but wouldn't 7 be the largest prime factor of 21? also, how come it only need to iterate to the square root of the number?

[fardeenpanjwani]

in euler2, the problem said fib number below 4 million. why did the sol have fib(10million)??

[nddonkj]

4)
def is_palindrome(num):
num = str(num)
return num == num[::-1]

def all_combinations(first, last):
base = []
for i in range(first, last):
for n in range(first, last):
r = i * n
if r not in base and is_palindrome(r):
base.append(r)
return base

print(max(all_combinations(10, 100)))

[ihsankundup]

hi thanks for your efforts,
i have a question for third question....
why did you say if len (factor(i))==0, not understand very well actually

[poketoscoparentesesloparen]

I tried to do euler 1 by hand but was too lazy, but here is my very efficient solution:
def sumMultiplesOf3or5(N):
return sumMultiplesOfKupToN(3, N) + sumMultiplesOfKupToN(5, N) - sumMultiplesOfKupToN(15, N)

def sumMultiplesOfKupToN(K, N):
n =(N-1)//K
sumNaturalsUpton = (n*(n+1))/2
return K*sumNaturalsUpton

[armandomendivil]

in euler 1 you're using O(N) complexity, you can solve that problem using O(1)

[brotherlui]

Problem 4: One could use itertools.combinations(range(100, 1000), 2) and the is_palindrome function is as simple as: return str(number) == str(number)[::-1] (i know this vid is over 2 years old and i assume you would code it this way by now, too. No pun intended.)

[Kingofqueers]

for the even fibonacci question why did you put "to = 10" as a parameter in the function

[nimmakayalakaushik]

Can you explain the for loop used in problem 3

[iKostanCom]

Interesting, but I made same mistakes... Thank you for the tutorial.

[jimjam]

You say that you don’t want 2 back from your prime factorization, but 2 is a prime number...

[subhambiswas]

Hey i am trying to solve with this method but not getting it 4th problem.
First i define is_palindrome function which returns true or false, and then calling two nested while loops from 10 to 100
and sending their product to is_palindrome function, if it returns true then appending that number to an empty list, afterwards i am calling max operator on that list, is this right way of doing it?

[mrmertozturk]

What is the name of the step we are doing at 15:50 ?

[asadullahfarooqi]

hey how many have you done on your own profile?

[ep]

for problem 1 my c++ program was around 8 times faster than his python solution (idea: utilize Gauß sum):
#include<bits/stdc++.h>
using namespace std;
int f(int n)
{
int sum=0, a=ceil((float)n/5.0)-1, b=ceil((float)n/3.0)-1, c=ceil((float)n/15.0)-1;
sum += 5*a*(a+1)/2;
sum += 3*b*(b+1)/2;
sum -= 15*c*(c+1)/2;
return sum;
}
int main()
{
printf("%d", f(1000));
return 1;
}

[ЭдвардЕвгенич]

Почему во второй задаче он поставил Увы английский только начал учить

[ylamummo]

Problem 3, I would have done the following (in C)
for (int i = 2; i*i <= n; i++) {
while(n%i == 0 && n != i) n /= i;
}
return n;