Created
June 8, 2012 03:22
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proj euler 12
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| (ns junk.core | |
| (:use clojure.test)) | |
| (defn check-prime [ps candidate] (every? #(not= 0 (mod candidate %)) ps)) | |
| (deftest check-prime-test | |
| (is (check-prime [2 3 5] 7)) | |
| (is (not (check-prime [2 3 5] 6)))) | |
| (defn next-prime [ps max] (first | |
| (filter #(check-prime ps %) | |
| (map (partial + max) (range))))) | |
| (deftest next-prime-test | |
| (is (= (next-prime [2] 2) 3))) | |
| (defn primes | |
| ([] (cons 2 (primes [2] 2))) | |
| ([ps max] | |
| (lazy-seq (let [np (next-prime ps max)] | |
| (cons np | |
| (primes | |
| (conj ps np) | |
| (inc max))))))) | |
| (deftest primes-test | |
| (is (= (first (primes)) 2)) | |
| (is (= (seq [2 3 5 7 11 13]) (seq (take 6 (primes)))))) | |
| (defn divides-times [n div] | |
| (loop [n' n count 0] | |
| (if (= 0 (mod n' div)) | |
| (recur (quot n' div) (inc count)) | |
| [n' count]))) | |
| (deftest divides-times-test | |
| (is (= (divides-times 6 2) [3 1])) | |
| (is (= (divides-times 6 5) [6 0]))) | |
| (defn find-divisors' [n ps] | |
| (reduce | |
| (fn [[n m] div] | |
| (let [[n' count] (divides-times n div)] | |
| (if (= count 0) | |
| [n' m] | |
| [n' (conj m [div count])]))) [n {}] ps)) | |
| (defn find-divisors [n ps] | |
| (second (find-divisors' n (take-while (partial > n) ps)))) | |
| (deftest find-divisors-test | |
| (let [ps (primes)] | |
| (is (= (find-divisors 28 ps) {7 1 2 2})))) | |
| (defn count-divisors [n ps] | |
| (apply * (map (partial + 1) (vals (find-divisors n ps))))) | |
| (deftest count-divisors-test | |
| (is (= (count-divisors 28 (primes)) 6))) | |
| (defn tris [n cur] (lazy-seq (cons n (tris (+ n cur) (inc cur))))) | |
| (deftest test-tris | |
| (is (= (take 5 (tris 1 2)) '(1 3 6 10 15)))) | |
| (defn find-solution [maxdivs ps] | |
| (first (filter #(< maxdivs (count-divisors % ps)) (tris 1 2)))) | |
| (defn -main | |
| "I don't do a whole lot." | |
| [& args] | |
| (let [ps (take 501 (primes)) | |
| soltri (find-solution 500 ps)] | |
| (println "sol " (str soltri)))) |
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