Project Euler

Problem: Find the largest product of any 13 adjacent digits in a 1000 digit number. Solution: Move through the 1000 digit number with a sliding window of 13 digits. For…

Problem: What is the 10,001st prime number? Q. How do we find the nth prime number?A. Build a Sieve of Eratosthenes large enough to contain the nth prime number. Q.…

Problem: Find the difference between the sum of the square of the first 100 natural numbers, and the square of the sum of the first 100 natural numbers. Solution: PHP…

Problem: Find the smallest number with all the integers 1 to 20 as factors (i.e. divisible without a remainder). Q. What is the simplest way to find the lowest number…

Problem: Find the longest palindrome made from the product of two three-digit numbers. Q: How do we work out if a number is a palindrome?A: Convert it to a string…

Problem: What is the highest prime factor of n? In this case: n = 600851475143 Q: What is the simplest way to find the highest prime factor of n?A: Try dividing…

Problem: Find the sum of all the even numbers in the Fibonacci sequence whose values do not exceed 4 million. Q: What is the minimum section of the sequence that…

Problem: Find the sum of all numbers below 1000 which are a multiple of 3 or 5. Solution: Given the numbers involved, we can simply brute-force the answer by simply…