/* Created for this code golf challenge: https://codegolf.stackexchange.com/questions/164439 The Time Anagram Originally posted (and deleted) by @Tlink, which was most likely inspired from this StackOverflow question. Since it was a shame it got deleted, because it seemed like a good challenge in general, I figured I'd repost it with proper formatting and rules. (I've tried contacting @Tlink and get his/her permission to post it, but (s)he doesn't respond any more, which is why I decided to post it myself now.) Input: Six digits. Output: Either the first or last valid time in the 24-hour format (00:00:00 through 23:59:59). (You can choose yourself whether you output the first or last valid time.) Example: When the inputs are 1,8,3,2,6,4, the following times can be created: 12:36:48 12:38:46 12:46:38 12:48:36 13:26:48 13:28:46 13:46:28 13:48:26 14:26:38 14:28:36 14:36:28 14:38:26 16:23:48 16:24:38 16:28:34 16:28:43 16:32:48 16:34:28 16:38:24 16:38:42 16:42:38 16:43:28 16:48:23 16:48:32 18:23:46 18:24:36 18:26:34 18:26:43 18:32:46 18:34:26 18:36:24 18:36:42 18:42:36 18:43:26 18:46:23 18:46:32 21:36:48 21:38:46 21:46:38 21:48:36 23:16:48 23:48:16 So we'll output either 12:36:48 or 23:48:16 in this case, being the first / last respectively. Challenge rules: State whether you output the first or last valid time in your answer. I/O is flexible. Input can be six separated integers; a string containing the six digits; an integer list/array; a single (possibly octal) number; etc. Output can be a correctly ordered list/array of digits; a String in the format HH:mm:ss/HHmmss/HH mm ss; every digit printed with new-line delimiter; etc. Your call. You are allowed to take the digits in any order you'd like, so they can already be sorted from lowest to highest or vice-versa. If no valid time can be created with the given digits (i.e. 2,5,5,5,5,5), make so clear in any way you'd like. Can return null/false; "Not possible"; crash with an error; etc. (You cannot output an invalid time like 55:55:52, or another valid time like 00:00:00.) Please state how it handles inputs for which no valid time can be created. You are not allowed to output all possible valid times. Only the earliest/latest should be outputted/returned. 24 for hours (i.e. 24:00:00), or 60 for minutes/seconds (i.e. 00:60:60) are not valid. The ranges are [00-23] for hours and [00-59] for minutes and seconds. General rules: This is code-golf, so shortest answer in bytes wins. Don't let code-golf languages discourage you from posting answers with non-codegolfing languages. Try to come up with an as short as possible answer for 'any' programming language. Standard rules apply for your answer, so you are allowed to use STDIN/STDOUT, functions/method with the proper parameters and return-type, full programs. Your call. Default Loopholes are forbidden. If possible, please add a link with a test for your code. Also, please add an explanation if necessary. Test cases: Input: Earliest output: Latest output: 1,2,3,4,6,8 12:36:48 23:48:16 2,5,5,5,5,5 None possible None possible 0,0,0,1,1,1 00:01:11 11:10:00 1,1,2,2,3,3 11:22:33 23:32:11 9,9,9,9,9,9 None possible None possible 2,3,5,5,9,9 23:59:59 23:59:59 1,2,3,4,5,6 12:34:56 23:56:41 0,0,0,0,0,0 00:00:00 00:00:00 1,5,5,8,8,8 18:58:58 18:58:58 1,5,5,5,8,8 15:58:58 18:58:55 1,1,1,8,8,8 18:18:18 18:18:18 389 bytes */ fun p(d:Array)={val s=Array(6,{0}) val f=Array(6,{1>0}) val t=Array(3,{0}) val o=Array(3,{60}) fun r(i:Int){if(i>5){var l=0>1 var e=!l for(p in 0..2){t[p]=s[p*2]*10+s[p*2+1] l=l||(e&&t[p]1 s[i]=d[p] r(i+1) f[p]=1>0}} r(0) if(o[0]>23)0 else "${o[0]}:${o[1]}:${o[2]}"}() // Expanded version to return string of earliest time. fun process(digits: Array) = { // Current sequence of digits being checked, set // of marks to show a digit is free to be used, // grouped time hour, minute, & second to be // tested, earliest time to be outputted. val sequence = Array(6, {0}) val free = Array(6, {1>0}) val test = Array(3, {0}) val output = Array(3, {60}) // Recursive function to try a combination. fun recurse(index: Int) { // If we have set a complete sequence, see if // it is the eariest so far. if (index > 5) { // For each of the time numbers (hour, minute, // & second), convert the sequence into it's // number and keeping track of it being less // than the current earliest time or still // equal. var less = 0>1 var equal = !less for (position in 0..2) { test[position] = sequence[position*2]* 10+sequence[position*2+1] less = less || (equal && test[position] < output[position]) equal = equal && test[position] == output[position] } // for // If the time is valid and less than the // current earliest, it becomes the new // earliest. if (test[0] < 24 && test[1] < 60 && test[2] < 60 && less) for (position in 0..2) output[position] = test[position] // Otherwise, try the next set of digits for // this index in the sequence. For each digit, // if it hasn't been used, remember we used it, // put it in the sequence, recurse to test it // out, and free it up when done. } else for (position in 0..5) if (free[position]) { free[position] = 0>1 sequence[index] = digits[position] recurse(index+1) free[position] = 1>0 } // if } // if // Start the recursive processing. If the output // time didn't find an earliest, return zero, // otherwise return the time. recurse(0) if (output[0]>23) 0 else "${output[0]}:${output[1]}:${output[2]}" }() // Process each of the test cases. fun main(args: Array) { val tests = arrayOf(arrayOf(1,2,3,4,6,8), arrayOf(2,5,5,5,5,5), arrayOf(0,0,0,1,1,1), arrayOf(1,1,2,2,3,3), arrayOf(9,9,9,9,9,9), arrayOf(2,3,5,5,9,9), arrayOf(1,2,3,4,5,6), arrayOf(0,0,0,0,0,0), arrayOf(1,5,5,8,8,8), arrayOf(1,5,5,5,8,8), arrayOf(1,1,1,8,8,8)) for (test in tests) { println(p(test)) } //for } // main

time cg