ruby-on-rails - 如何将整数转换为二进制数组...

Question

谁能给出最简单的解决方案，将整数转换为表示其相关二进制数字的整数数组..

Input  => Output
1      => [1]
2      => [2]
3      => [2,1]
4      => [4]
5      => [4,1]
6      => [4,2]

One way is :
Step 1 : 9.to_s(2) #=> "1001"
Step 2 : loop with the count of digit
         use / and % 
         based on loop index, multiply with 2
         store in a array

有没有其他直接或更好的解决方案？

Answer 1

Fixnum 和 Bignum 有一个 [] 方法，它返回第 n 位的值。有了这个我们可以做

def binary n
  Math.log2(n).floor.downto(0).select {|i| n[i] == 1 }.collect {|i| 2**i}
end

您可以通过计算 2 的连续幂直到该幂太大来避免调用 Math.log2:

def binary n
  bit = 0
  two_to_the_bit = 1
  result = []
  while two_to_the_bit <= n
    if n[bit] == 1
      result.unshift two_to_the_bit
    end
    two_to_the_bit = two_to_the_bit << 1
    bit += 1
  end
  result
end

更冗长，但更快