// Created for this challenge: // https://www.sololearn.com/post/128588 // Here's an interesting challenge for those // interested: find my number! // I will leave the clues here, and your job // is to write a program to figure out the // number! Seems simple enough right? Cool! // Let's have some fun! // Between 1 and 1000, there is only 1 number // that meets the following criteria: // 1. The number has two or more digits. // 2. The number is prime. // 3. The number does NOT contain a 1 or 7 in // it. // 4. The sum of all of the digits is less // than or equal to 10. // 5. The first two digits add up to be odd. // *6. The second to last digit is even and // greater than 1. // 7. The last digit is equal to how many // digits are in the number. // So what's my number? Programs are better // than proofs here! {^_^} // *Clarification: (So if the number is 2 or // 3 digits, you want the digit in the 10s // spot) // Function to split the number into digits. // Make a mutable copy of the number and // an empty list. While the copy has more // digits, add the current digit to the // front of the list and remove it from // the copy. Once we are done finding digits, // return an unmutable copy of the finished // list. fun breakNumber(number: Int): List { var value = number val list = MutableList(0) { 0 } while (value > 0) { list.add(0, value%10) value /= 10 } // while return list.toList() } // breakNumber // Function to get all primes below 1000. // Make an empty list. For all possible // values from 2 to 1000, for all primes // that have been found so far, if the // value can be evenly divided by the prime, // it can't be a prime so abort our prime // loop and get the next value. If our // prime loop finishes without finding a // factor, our value must be a prime so // add it to our list. Once we are done // checking values, return an unmutable copy // of the finished list. fun getPrimes(): List { val list = MutableList(0) { 0 } outer@ for (value in 2..1000) { for (prime in list) if (value%prime == 0) continue@outer list.add(value) } // for return list.toList() } // getPrimes // Function to check the following statement: // 1. The number has two or more digits. fun statement1(digits: List) = digits.size >= 2 // Function to check the following statement: // 2. The number is prime. fun statement2(number: Int, primes: List) = number in primes // Function to check the following statement: // 3. The number does NOT contain a 1 or 7 in // it. fun statement3(digits: List) = 1 !in digits && 7 !in digits // Function to check the following statement: // 4. The sum of all of the digits is less // than or equal to 10. fun statement4(digits: List) = digits.sum() <= 10 // Function to check the following statement: // 5. The first two digits add up to be odd. fun statement5(digits: List) = (digits[0]+digits[1])%2 == 1 // Function to check the following statement: // *6. The second to last digit is even and // greater than 1. fun statement6(digits: List): Boolean { val digit = digits[digits.size-2] return digit%2 == 0 && digit > 1 } // statement6 // Function to check the following statement: // 7. The last digit is equal to how many // digits are in the number. fun statement7(digits: List) = digits.size == digits[digits.size-1] // Main function for this challenge. Get a // list of all primes in our range. For // all numbers in our range, break the // number into a list of digits, and if // all seven statements are true, we found // our winner so display it. Most statements // need the digit list. One needs the number // and primes list. fun main(args: Array) { val primes = getPrimes() for (number in 1..1000) { val digits = breakNumber(number) if (statement1(digits) && statement2(number, primes) && statement3(digits) && statement4(digits) && statement5(digits) && statement6(digits) && statement7(digits)) println(number) } // for } // main

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