## October 4, 2008

at
Saturday, October 04, 2008
Labels:
Computer Science,
Lisp,
Project Euler
Posted by
Billy

The sum of the squares of the first ten natural numbers is,

12 + 22 + ... + 102 = 385

The square of the sum of the first ten natural numbers is,

(1 + 2 + ... + 10)2 = 552 = 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.

A simple, straight forward solution in common lisp:

;;; Project Euler Problem 6

(defun sum-of-squares (upper-limit)

(loop for i from 1 to upper-limit sum (* i i)))

(defun square-of-sum (upper-limit)

(expt (loop for i from 1 to upper-limit sum i)

2))

(defun difference (upper-limit)

(- (square-of-sum upper-limit)

(sum-of-squares upper-limit)))

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