Look-and-say sequence
Sequence Definition
- Take a decimal number
- Look at the number, visually grouping consecutive runs of the same digit.
- Say the number, from left to right, group by group; as how many of that digit there are - followed by the digit grouped.
You are encouraged to solve this task according to the task description, using any language you may know.
- This becomes the next number of the sequence.
The sequence is from John Conway, of Conway's Game of Life fame.
An example:
- Starting with the number 1, you have one 1 which produces 11.
- Starting with 11, you have two ones i.e. 21
- Starting with 21, you have one two, then one 1 i.e. 1211
- Starting with 1211 you have one 1, one 2, then two 1's i.e. 111221
Write a program to generate successive members of the look-and-say sequence.
Python
<lang python>>>> from itertools import groupby >>> concat = .join >>> def lookandsay(number): return concat( concat([str(len(list(g))), k]) for k,g in groupby(number) )
>>> numberstring='1' >>> for i in range(10): print numberstring numberstring = lookandsay(numberstring)
1 11 21 1211 111221 312211 13112221 1113213211 31131211131221 13211311123113112211 >>> </lang>