How to check that only one value in an array is non-zero?

Given an array like : [0,1,1]

How can I elegantly check that: Only one element has a non-zero value and that the others are 0?

(So the above array will fail the check while this array will pass : [开发者_如何转开发1,0,0])

my_array.count(0) == my_array.length-1

If speed is important, for very large arrays where you might need to return early upon detecting a second non-zero, perhaps:

def only_one_non_zero?( array )
  found_non_zero = false
  array.each do |val|
    if val!=0
      return false if found_non_zero
      found_non_zero = true
    end
  end
  found_non_zero
end

Select at most two non-zero elements, and check if exactly one item was available.

>> [0,1,1].select {|x| !x.zero?}.take(2).size == 1
=> false
>> [0,1,0].select {|x| !x.zero?}.take(2).size == 1
=> true
>> [1,2,3].select {|x| !x.zero?}.take(2).size == 1
=> false

Works fine in Ruby 1.8.7, but note that select returns an array, so it's not "optimally lazy". Here's a blog post showing how to make some lazy enumerators in Ruby.

Thanks for all your answers!

I solved too:

input_array = [0,0,0]
result = input_array - [0]
p result.size == 1 && result[0] == 1

Ruby, I love you!