diff --git a/project_euler/problem_006/sol1.rb b/project_euler/problem_006/sol1.rb new file mode 100644 index 0000000..b00c9e7 --- /dev/null +++ b/project_euler/problem_006/sol1.rb @@ -0,0 +1,32 @@ +#Project Euler Problem 6: #https://projecteuler.net/problem=6 + +#Sum square difference + +#The sum of the squares of the first ten natural numbers #is, +# 1^2 + 2^2 + ... + 10^2 = 385 +#The square of the sum of the first ten natural numbers #is, +# (1 + 2 + ... + 10)^2 = 55^2 = 3025 +#Hence the difference between the sum of the squares of #the first ten +#natural numbers and the square of the sum is 3025 - 385 = 2640. +#Find the difference between the sum of the squares of the first one +#hundred natural numbers and the square of the sum. + +def solution(num=10) + x = 1 + y = 1 + result = 1 + gap = 3 + while y < num + x += gap + gap += 2 + y += 1 + result += x + end + r_n_pow2_plus_n_pow2 = result + r_sum_n_pow2 = (((num / 2) + 0.5) * num) ** 2 + + r_sum_n_pow2 - r_n_pow2_plus_n_pow2 +end + +answer = solution() +p answer