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Recursive Puzzle Solver
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| /* | |
| http://richardwiseman.wordpress.com/2014/08/04/answer-to-the-friday-puzzle-269/ | |
| OK, onto the puzzle. Can you create a 10-digit number, | |
| where the first digit is how many zeros in the number, | |
| the second digit is how many 1s in the number etc | |
| until the tenth digit which is how many 9s in the number. | |
| */ | |
| def selfReferential(number:String) : Boolean = { | |
| val numsWithIdx=number.zipWithIndex | |
| numsWithIdx.forall( nIdx => number.count(_.asDigit==nIdx._2)==nIdx._1.asDigit) | |
| } //> selfReferential: (number: String)Boolean | |
| val seed="9000000000" //> seed : String = 9000000000 | |
| def correct(s:String):String = { | |
| if(selfReferential(s)) s | |
| else { | |
| val counts=0.to(9).map(idx=>s.count(_.asDigit==idx)) | |
| println(counts.mkString) | |
| val newCandidate=counts.mkString | |
| correct(newCandidate) | |
| } | |
| } //> correct: (s: String)String | |
| correct(seed) //> 9000000001 | |
| //| 8100000001 | |
| //| 7200000010 | |
| //| 7110000100 | |
| //| 6300000100 | |
| //| 7101001000 | |
| //| 6300000100 | |
| //| 7101001000 | |
| //| 6300000100 | |
| //| 7101001000 | |
| //| 6300000100 | |
| // and so on! |
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