# Crazy Librarian's Interesting Prime Permutation Index Number Generator

You saved the day with your prime sequence code, and the math teacher loved it. So much so that a new challenge was posed to the librarian (a/k/a, your boss). Congratulations, you get to code the solution so the librarian can once again impress the math teacher.

0, 1, 2, 3, 4, 5, 6 ...

Excluding 0 and 1, every number in this sequence either is prime, P

2, 3, 5, 7, 11, 13 ...

or composite, C

4, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20 ...

Reflecting on how the librarian thought to insert an integer digit into the decimal expansion of a number from P, the math teacher instead created a function G(x,y) that takes a number x from N with 1 <= x <= 9 and a number y from C and inserts x into the decimal expansion of y in every position, in order left-to-right, selecting only unique numbers.

For example, G(3,14) is 314, 134, 143. However, G(1,14) is only 114, 141, as whether you prepend or insert the 1 into 14, the same number 114 is generated.

The math teacher wondered how many times you'd have to do these permutations before you get a number that's in P, if you took x in increasing order. The math teacher called this the Composite-Prime Index of a number, and wrote it as CPI(y).

For example, 4 only needs to be done twice: 14, 41, since 41 is prime, so CPI(4) is 2. However, 8 needs to be done 6 times, 18, 81, 28, 82, 38, 83 before reaching 83 as a prime number, so CPI(8) is 6.

Your task is to write code that will output this Composite-Prime Index, given an input number.

## Input

• A single integer y, such that y is in C, input via function argument, STDIN, or equivalent.
• For the purposes of calculation, you can assume y will fit in usual integer ranges (e.g., assume 231-1 as an upper bound).
• Behavior for y not in C is undefined.

## Output

The resultant Composite-Prime Index, calculated as described above, output to STDOUT or equivalent, with two exceptions:

• If the very last permutation (i.e., appending 9 to y) is the one that results in a prime, output -1. An example, expanded below, is y=14.
• If there is no permutation (i.e., G(x,y) is a subset of C for all 1 <= x <= 9), output 0. An example, expanded below, is y=20.

## Examples

 y -> operations             : output
4 -> 14, 41                 : 2
6 -> 16, 61                 : 2
8 -> 18, 81, 28, 82, 38, 83 : 6
9 -> 19                     : 1
10 -> 110, 101               : 2
12 -> 112, 121, 212, 122, 312, 132, 123, 412, 142, 124, 512, 152, 125, 612, 162, 126, 712, 172, 127 : 19
14 -> 114, 141, 214, 124, 142, 314, 134, 143, 414, 144, 514, 154, 145, 614, 164, 146, 714, 174, 147, 814, 184, 148, 914, 194, 149 : -1
15 -> 115, 151               : 2
16 -> 116, 161, 216, 126, 162, 316, 136, 163 : 8
18 -> 118, 181               : 2
20 -> 120, 210, 201, 220, 202, 320, 230, 203, 420, 240, 204, 520, 250, 205, 620, 260, 206, 720, 270, 207, 820, 280, 208, 920, 290, 209 : 0


## Restrictions

• This is code-golf, since you'll need to transcribe this to an index card so the librarian can show the math teacher, and your hand cramps easily.
• Standard loophole restrictions apply. The librarian doesn't tolerate cheaters.

var QUESTION_ID=63191,OVERRIDE_USER=42963;function answersUrl(e){return"http://api.stackexchange.com/2.2/questions/"+QUESTION_ID+"/answers?page="+e+"&pagesize=100&order=desc&sort=creation&site=codegolf&filter="+ANSWER_FILTER}function commentUrl(e,s){return"http://api.stackexchange.com/2.2/answers/"+s.join(";")+"/comments?page="+e+"&pagesize=100&order=desc&sort=creation&site=codegolf&filter="+COMMENT_FILTER}function getAnswers(){jQuery.ajax({url:answersUrl(answer_page++),method:"get",dataType:"jsonp",crossDomain:!0,success:function(e){answers.push.apply(answers,e.items),answers_hash=[],answer_ids=[],e.items.forEach(function(e){e.comments=[];var s=+e.share_link.match(/\d+/);answer_ids.push(s),answers_hash[s]=e}),e.has_more||(more_answers=!1),comment_page=1,getComments()}})}function getComments(){jQuery.ajax({url:commentUrl(comment_page++,answer_ids),method:"get",dataType:"jsonp",crossDomain:!0,success:function(e){e.items.forEach(function(e){e.owner.user_id===OVERRIDE_USER&&answers_hash[e.post_id].comments.push(e)}),e.has_more?getComments():more_answers?getAnswers():process()}})}function getAuthorName(e){return e.owner.display_name}function process(){var e=[];answers.forEach(function(s){var r=s.body;s.comments.forEach(function(e){OVERRIDE_REG.test(e.body)&&(r="<h1>"+e.body.replace(OVERRIDE_REG,"")+"</h1>")});var a=r.match(SCORE_REG);a&&e.push({user:getAuthorName(s),size:+a,language:a,link:s.share_link})}),e.sort(function(e,s){var r=e.size,a=s.size;return r-a});var s={},r=1,a=null,n=1;e.forEach(function(e){e.size!=a&&(n=r),a=e.size,++r;var t=jQuery("#answer-template").html();t=t.replace("{{PLACE}}",n+".").replace("{{NAME}}",e.user).replace("{{LANGUAGE}}",e.language).replace("{{SIZE}}",e.size).replace("{{LINK}}",e.link),t=jQuery(t),jQuery("#answers").append(t);var o=e.language;/<a/.test(o)&&(o=jQuery(o).text()),s[o]=s[o]||{lang:e.language,user:e.user,size:e.size,link:e.link}});var t=[];for(var o in s)s.hasOwnProperty(o)&&t.push(s[o]);t.sort(function(e,s){return e.lang>s.lang?1:e.lang<s.lang?-1:0});for(var c=0;c<t.length;++c){var i=jQuery("#language-template").html(),o=t[c];i=i.replace("{{LANGUAGE}}",o.lang).replace("{{NAME}}",o.user).replace("{{SIZE}}",o.size).replace("{{LINK}}",o.link),i=jQuery(i),jQuery("#languages").append(i)}}var ANSWER_FILTER="!t)IWYnsLAZle2tQ3KqrVveCRJfxcRLe",COMMENT_FILTER="!)Q2B_A2kjfAiU78X(md6BoYk",answers=[],answers_hash,answer_ids,answer_page=1,more_answers=!0,comment_page;getAnswers();var SCORE_REG=/<h\d>\s*([^\n,]*[^\s,]),.*?(\d+(?:[.]\d+)?)(?=[^\n\d<>]*(?:<(?:s>[^\n<>]*<\/s>|[^\n<>]+>)[^\n\d<>]*)*<\/h\d>)/,OVERRIDE_REG=/^Override\s*header:\s*/i;
body{text-align:left!important}#answer-list,#language-list{padding:10px;width:290px;float:left}table thead{font-weight:700}table td{padding:5px}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <link rel="stylesheet" type="text/css" href="//cdn.sstatic.net/codegolf/all.css?v=83c949450c8b"> <div id="answer-list"> <h2>Leaderboard</h2> <table class="answer-list"> <thead> <tr><td></td><td>Author</td><td>Language</td><td>Size</td></tr></thead> <tbody id="answers"> </tbody> </table> </div><div id="language-list"> <h2>Winners by Language</h2> <table class="language-list"> <thead> <tr><td>Language</td><td>User</td><td>Score</td></tr></thead> <tbody id="languages"> </tbody> </table> </div><table style="display: none"> <tbody id="answer-template"> <tr><td>{{PLACE}}</td><td>{{NAME}}</td><td>{{LANGUAGE}}</td><td>{{SIZE}}</td><td><a href="{{LINK}}">Link</a></td></tr></tbody> </table> <table style="display: none"> <tbody id="language-template"> <tr><td>{{LANGUAGE}}</td><td>{{NAME}}</td><td>{{SIZE}}</td><td><a href="{{LINK}}">Link</a></td></tr></tbody> </table>

• For 9, 19 is prime, so shouldn't the output be 1? – isaacg Nov 7 '15 at 9:10
• Wow, cool answer chart! – cascading-style Dec 17 '16 at 3:41
• @cascading-style If you mean the Leaderboard, that's primarily Martin's handiwork. – AdmBorkBork Dec 17 '16 at 7:02

# Pyth, 35 bytes

&sKm}dPdsm{msjdcz]khlzS9|%hxK1lK_1


Test suite

p n=mod(product[1..n-1]^2)n>0
n#c=[h++c:t|i<-[0..length n],(h,t)<-[splitAt i n]]
[y]%i|q y= -1|1<2=0
(y:z)%i|q y=i|1<2=z%(i+1)
f n=((n#)=<<['1'..'9'])%1


Usage examples: f "8" -> 6, f "14"-> -1, f "20"-> 0.

How it works: p is the primality test (stolen from @Mauris' answer in a different challenge). q a wrapper for p to convert types from strings to integer. n # c inserts c at every position in n. % takes a list of numbers and an index i. When the first element of the list is prime, return i, else recure with the tail of the list and i+1. Stop when there's a single element left and return -1 if it's prime and 0 otherwise.

## Minkolang 0.11, 85 bytes

n1(l*$d)d9[i3G(0c2c$%$r2c*l*2c3c1+*++2gl:d2G)2gx1c2G3gx]r3XS(2M4&I)N.ikI1-4&1~N.1+N.  Try it here. ### Explanation (coming soon) n Take integer from input (say, n) 1( Calculate smallest power of 10 greater than n (say, a) l* Multiply by 10$d      Duplicate stack and push n>a
)     Close while loop (ends when n<=a)
d    Duplicates a (let's call it b)

9[                                                 For loop that runs 9 times
i1+                                              Loop counter + 1 (say, i)
3G                                            Puts the loop counter in position 3
(                                           Opens while loop
0c2c$% Copies n and b and pushes n//b, n%b$r                                   Swaps top two elements of stack
2c*l*                              Copies b and multiplies by 10
2c3c*                         Copies b and i and multiplies them
++                       Adds it all together (inserts i)
2gl:                   Gets b and divides by 10
d2G                Duplicates and puts one copy back
)               Closes while loop (breaks when b=0)
2gx            Gets and dumps b
1c2G        Copies a and puts it in b's place
3gx     Get and dumps i
]    Close for loop

r       Reverses stack
3X     Dumps the top three elements (namely, n, a, and b)
S    Removes duplicates

(                           Opens while loop
2M                         Pushes 1 if top of stack is prime, 0 otherwise
4&                       Jump four spaces if prime
I)N.                   If the loop actually finishes, then all were composite,
so output 0 and stop.
ik                 Pushes loop counter and breaks
I1-              Pushes length of stack minus 1 (0 if last one was prime)
4&1~N.        If this is 0, pushes -1, outputs as integer, and stops.
1+N.    Adds 1, outputs as integer, and stops.


# Javascript, 324 bytes

y=>(p=(n,c)=>n%c!=0?c>=n-1?1:p(n,++c):0,u=a=>a.filter((c,i)=>a.indexOf(c)==i),g=(x,y)=>u(((x,y,z)=>z.map((c,i)=>z.slice(0,i).join("")+x+z.slice(i).join("")).concat(y+x))(x,y,y.split(''))),h=(x,y)=>g(x,y).concat(x==9?[]:h(++x,y)),i=h(1,y).reduce((r,c,i)=>r?r:p(c,2)?i+1:0,0),console.log(p(y,2)||y<2?'':i==h(1,y).length?-1:i))


If y not in C, then STDOUT output is empty.

## Explanation

y=>(
//Prime Test function
p=(n,c)=>n%c!=0?c>=n-1?1:p(n,++c):0,

//Unique function
u=a=>a.filter((c,i)=>a.indexOf(c)==i),

//Generates numbers from a couple x and y
g=(x,y)=>u(((x,y,z)=>z.map((c,i)=>z.slice(0,i).join("")+x+z.slice(i).join("")).concat(y+x))(x,y,y.split(''))),

//Generates all possible numbers from y using recusion
h=(x,y)=>g(x,y).concat(x==9?[]:h(++x,y)),

//Check if any prime in the generated numbers
i=h(1,y).reduce((r,c,i)=>r?r:p(c,2)?i+1:0,0),

console.log(
//Is Y in C ?
p(y,2)||y<2?
''
:
// Check if the answer is not the last one
i==h(1,y).length?-1:i)
)

• Might be very late on commenting this, but couldn't you save a few bytes by replacing n%c!=0 with n%c; c>=n-1 with c>n-2; and x==9 with x-9`? – Zacharý Nov 26 '16 at 16:57