Given an n x m array of boolean:
[[true, true, false],
[false, true, true],
[false, true, true]]
what is the shortest code that can return "how many true are there in that column?"
the result should be
[1, 3, 2]
views:
96answers:
4
+6
A:
Use transpose to get an array where each subarray represents a column and then map each column to the number of trues in it:
arr.transpose.map {|subarr| subarr.count(true) }
Here's a version with inject that should run on 1.8.6 without any dependencies:
arr.transpose.map {|subarr| subarr.inject(0) {|s,x| x ? s+1 : s} }
sepp2k
2010-08-01 12:36:25
wow works in Ruby 1.9.1. Is there a solution for 1.8.6?
動靜能量
2010-08-01 12:40:49
It works in 1.8.7, too. For 1.8.6 you can probably get the count method from backports or active_support. If that's not an option, you can write it using inject.
sepp2k
2010-08-01 12:42:29
Elegant, but not very verbose. +1 anyway.
You
2010-08-01 12:53:29
seems like you can also use: count(true)instead of: count{|x| x}
Ragmaanir
2010-08-01 13:03:12
@Ragmaanir: Nice. Good suggestion.
sepp2k
2010-08-01 13:07:02
A:
array = [[true, true, false],
[false, true, true],
[false, true, true]]
array.transpose.map {|x| x.count {|y| y}}
igorgue
2010-08-01 12:42:01
A:
Here's another solution:
b.transpose.collect{|x| x.reject{|y| y != true}.length}
You
2010-08-01 12:45:34
A:
a=[[true, true, false],
[false, true, true],
[false, true, true]]
a.transpose.map{|c|c.count(true)}
sneaky way of saving one more character
a.transpose.map{|c|c.count(!!0)}
As Jonas points out it is possible to golf this some more
a.transpose.map{|c|c.count !!0}
gnibbler
2010-08-01 13:26:16