projecteuler.net problems

1.py

print sum([x for x in xrange(1000) if x%3==0 or x%5==0])

10.py

def primes(limit):
    is_prime = [False] * 2 + [True] * (limit - 1)
    for n in xrange(limit+1):
        if is_prime[n]:
            yield n
            for i in xrange(n*2, limit+1, n):
                is_prime[i] = False
print sum(primes(2000000))

2.py

fibs = {1: 1, 2:2}
def fib(n):
    if n in fibs:
        return fibs[n]
    fibs[n] = fib(n-1) + fib(n-2)
    return fibs[n]
num = 1
total = 0
limit = 4000000
next = 0
while next <= limit:
    next = fib(num)
    if next %2 ==0:
        total += next
    num+=1
print total

3.c

#include <stdio.h>

int isPrime(long long n)
{
	long long d = 2;
	while(d < n)
	{
		if(n%d==0)
		{
			return 0;
		}
		d++;
	}
	return 1;
}
long long largestPrimeFactor(long long n)
{
	long long d = 3;
	while(d < n)
	{
		if(n%d==0)
		{
			if(isPrime(n/d))
			{
				return n/d;
			}
		}
		d += 2;
	}
	return 0;
}
int main()
{
	printf("%lld \n", largestPrimeFactor(600851475143));
	return 0;
}

3.py

def is_prime(n):
    d = 2
    while d < n:
        if n%d==0:
            return False
        d+=1
    return True

def largest_prime_factor(n):
    potential_factor = 3
    while potential_factor < n:
        if n%potential_factor==0:
            if is_prime(n/potential_factor):
                return n/potential_factor
        potential_factor += 2
    return None

print largest_prime_factor(600851475143)

4.py

# Largest palindrome made from product of two 3-digit

def is_palindrome(n):
    s = str(n)
    if len(s) < 2:
        return False
    for x in xrange(len(s)/2):
        if s[x] != s[-(x+1)]:
            return False
    return True

pals = []
for n in xrange(100, 999):
    for j in xrange(100, 999):
        val = n * j
        if is_palindrome(val):
            pals.append(val)
print max(pals)

5.py

# Smallest positive number that is evenly disible by all numbers 1-20
def is_div_20(n):
    for x in xrange(2, 20):
        if n%x != 0:
            return False
    return True
n = 2
while is_div_20(n)==False:
    n += 2
print n 

6.py

'''
difference between the sum of the squares of the first
one hundred natural numbers and the square of the sum
'''

print abs(sum([x**2 for x in xrange(1, 101)])-(sum([x for x in xrange(1, 101)])**2))

7.py

def is_prime(n):
    d = 2
    while d < n:
        if n%d==0:
            return False
        d+=1
    return True
primes = 2
counter = 3
while primes < 10001:
    counter += 2
    if is_prime(counter):
        primes += 1 
print counter

8.py

#  Largest product of 5 consecute digits

nums = map(lambda x: int(x), list("3167176531330624919225119674426574742355349194934\
96983520312774506326239578318016984801869478851843\
85861560789112949495459501737958331952853208805511\
12540698747158523863050715693290963295227443043557\
66896648950445244523161731856403098711121722383113\
62229893423380308135336276614282806444486645238749\
30358907296290491560440772390713810515859307960866\
70172427121883998797908792274921901699720888093776\
65727333001053367881220235421809751254540594752243\
52584907711670556013604839586446706324415722155397\
53697817977846174064955149290862569321978468622482\
83972241375657056057490261407972968652414535100474\
82166370484403199890008895243450658541227588666881\
16427171479924442928230863465674813919123162824586\
17866458359124566529476545682848912883142607690042\
24219022671055626321111109370544217506941658960408\
07198403850962455444362981230987879927244284909188\
84580156166097919133875499200524063689912560717606\
05886116467109405077541002256983155200055935729725\
71636269561882670428252483600823257530420752963450"))

products = [nums[i]*nums[i+1]*nums[i+2]*nums[i+3]*nums[i+4] for i in xrange(len(nums) - 5)]
print max(products)

9.py

def find_triplet():
    for a in xrange(1, 1000):
        for b in xrange(1, 1000):
            for c in xrange(1, 1000):
                if a+b+c == 1000:
                    if a**2 + b**2 == c**2:
                        return a*b*c
print find_triplet()

Good3.py

# Largest prime factor of...
def prime_factors(n):
    factors = []
    d =2
    while n > 1:
        while n%d == 0:
            factors.append(d)
            n /= d
        d += 1
    return factors

print max(prime_factors(600851475143))