# ScalaEuler / src / com / mklinke / euler / Problem41.scala

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82``` ```/** * * * Copyright 2012 Martin Klinke, http://www.martinklinke.com. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package com.mklinke.euler /** * @author Martin Klinke * */ object Problem41 { def main(args: Array[String]) { val start = System.currentTimeMillis; for (i <- (1 to 9).reverse) { val it = findAllPandigitalPrimes(i) if (it.hasNext) println("n = " + i + ", max pandigital prime: " + it.max) } println("Duration: " + (System.currentTimeMillis - start) + " ms"); } def findAllPandigitalPrimes(n: Int): Iterator[Long] = { val permutations = (1 to n).permutations findPandigitalPrimes(permutations).iterator } def findPandigitalPrimes(it: Iterator[IndexedSeq[Int]]): Stream[Long] = { def loop(it: Iterator[IndexedSeq[Int]]): Stream[Long] = { if (it.hasNext) { val current = it.next.mkString.toLong if (isPrime(current)) current #:: loop(it) else loop(it) } else { Stream.empty } } loop(it) } val expectedSum = (1 to 9).sum val expectedProduct = (1 to 9).product def isPandigital(n: String): Boolean = { val digits = n.toList.map(c => c - 48) digits.sum == expectedSum && digits.product == expectedProduct } def isPrime(n: Long): Boolean = { if (n == 1) false else n == smallestDivisor(n) } def smallestDivisor(n: Long): Long = { findDivisor(n, 2) } def findDivisor(n: Long, testDivisor: Long): Long = { if (testDivisor * testDivisor > n) n else if (n % testDivisor == 0) testDivisor else findDivisor(n, testDivisor + 1) } } ```