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ScalaEuler / src / com / mklinke / euler / Problem36.scala

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/**
 * *
 *  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 Problem36 {

  def main(args: Array[String]): Unit = {
    val start = System.currentTimeMillis;
    println("Sum of decimal and binary palindromes: " + sumPalins(1, 1000000, 0))
    println("Duration: " + (System.currentTimeMillis - start) + " ms");
  }

  def sumPalins(currentN: Int, maxN: Int, currentSum: Int): Int = {
    if (currentN >= maxN)
      currentSum
    else
      sumPalins(currentN + 1, maxN, currentSum + (if (isDecimalPalindrome(currentN) && isBinaryPalindrome(currentN)) currentN else 0))
  }

  def isDecimalPalindrome(n: Int): Boolean = {
    isPalindrome(n.toString.toList.map(c => c - 48))
  }

  def isBinaryPalindrome(n: Int): Boolean = {
    isPalindrome(n.toBinaryString.toList.map(c => c - 48))
  }

  def isPalindrome(n: List[Int]): Boolean = { n == n.reverse }
}