Checking my attempt with the function in the essay cited, I see that
there's a misprint there.
The value of i should be '1113213211', not '1113122113', assuming i is
meant to be
,@((# , {.);.1~ (~: |.!.0))^:7 "."0 ,'1' NB. numeric result...
1 1 1 3 2 1 3 2 1 1
It's always good to learn - I hadn't noticed the useful idiom |.!.0 before.
So, fwiw, my attempt was, working on a numeric vector rather than a string,
,@:((# , ~.);.1)~ (1 , 2 ~:/\ ])
I suspect (1 , 2 ~:/\ ]) is less efficient than that idiom, and realise
that {.
does less work than ~.
Thanks,
Mike
On 02/09/2016 10:09, Henry Rich wrote:
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@.('1'&=@:{.))
twos=. (3 : '2&}.y')[(tt`to@.('1'&=@:{.))
f=. (ones`twos@.((0&{) = (1&{)))`ones@.(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?
----------------------------------------------------------------------
For information about J forums see http://www.jsoftware.com/forums.htm
----------------------------------------------------------------------
For information about J forums see http://www.jsoftware.com/forums.htm
---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
----------------------------------------------------------------------
For information about J forums see http://www.jsoftware.com/forums.htm
