用clojure解决 euler problem 6

问题描述：

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.

(ns euler-problem-6.core  (:use [clojure.contrib.math]))(defn square  [num]  (* num num))(square 3)(defn square-sum-version-1  [num]  (loop      [current-num 1M sum 0M]    (if (= current-num num)      (+ sum (square current-num))      (recur (inc current-num) (+ sum (square current-num))))))(defn square-sum-version-2  [num]  (reduce + (map square (range 1M (inc num)))));(time (square-sum-version-1 1000000M));(time (square-sum-version-2 1000000M))(defn sum-square-version-1  [num]  (loop      [current-num 1M add-sum 0M]    (if (= current-num num)      (square (+ add-sum current-num))      (recur (inc current-num) (+ current-num add-sum)))))(defn sum-square-version-2  [num]  (square (reduce + (range 1M (inc num)))));(sum-square-version-1 10);(sum-square-version-2 10)(defn dif-sum-square-with-square-sum  [num]  (abs (- (sum-square-version-1 num) (square-sum-version-1 num))))(dif-sum-square-with-square-sum 100M)

经测试，尾递归版本的性能要好于延迟加载的版本，但是延迟加载程序简单明了！