[Jprogramming] Count and say

[Henry Rich]

See http://code.jsoftware.com/wiki/Essays/Advent_Of_Code#Part_1_10

Henry Rich

On 9/2/2016 12:42 AM, 'Jon Hough' via Programming wrote:
> This is a leetcode question:
> https://leetcode.com/problems/count-and-say/
> Description:
> The count-and-say sequence is the sequence of integers beginning as follows:
> 1, 11, 21, 1211, 111221, ...
>
> 1 is read off as "one 1" or 11.
> 11 is read off as "two 1s" or 21.
> 21 is read off as "one 2, then one 1" or 1211.
> Given an integer n, generate the nth sequence.
>
> Note: The sequence of integers will be represented as a string.
>
> I thought it would be fun to tackle this in J...
>
>
>
> NB. Leetcode algorithm problem 38. Count and Say
> countandsay =: 3 : 0
> max=: y
> str=: ''
> tt=. 3 :'str=:str,''22'''
> to=. 3 :'str=:str,''21'''
> ot=. 3 :'str=:str,''12'''
> oo=. 3 :'str=:str,''11'''
>
> ones=. (3 : '1&}.y')[(ot`oo at .('1'&=@:{.))
> twos=. (3 : '2&}.y')[(tt`to at .('1'&=@:{.))
> f=. (ones`twos at .((0&{) = (1&{)))`ones at .(1&=@:#)^:(0&<@:#)^:_
> ctr=: 0
> val=. ((3 : 'str')[f)^:(3 : 'ctr<max[str=:''''[ctr=:>:ctr')^:_ '1'
> )
>
> countandsay 5 NB. test value 5
>
> My main goal for this solution was figuring out how to do it with no while or for loops.
> Anything more terse?
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