以2的幂的和以升序打印数字 [英] Printing a number as a sum of powers of 2 in increasing order

问题描述

我试图打印出一个十进制整数(非负数)作为2的幂的和，即输入10，它应该打印不带引号的"2 8".我已经写了这段代码，但是有人可以给我一个衬里吗.

I am trying to print out a decimal integer(non-negative) as sum of powers of 2 i.e for input 10, it should print "2 8" without quotes. I already wrote this code, but can someone give me a one liner for this.

n = bin(int(raw_input()))[-1:1:-1]
print (' ').join([str((int(n[j])+1)**j) for j in xrange(len(n)) if n[j] == '1'])

推荐答案

最好将其分布在多个行中，并且在列表理解中使用和input会隐藏代码内容的关键信息做.

It much better to have this spread across muplitple lines, and using and input inside a list comprehension hides a key piece of the information of what your code is doing.

最终，您要执行的操作看起来并不漂亮，但无论如何，这是应该的:

Ultimately, what you are asking to doisn't pretty, but here it is anyway:

print (' ').join([str(2**i) for i,j in enumerate(bin(int(raw_input()))[-1:1:-1]) if j == '1'])

精美印刷是:

print ' '.join(
    [str(2**i)
     for i,j in enumerate(
         bin(int(raw_input()))[-1:1:-1]
       )
      if j == '1']
  )

注意:

• int(n[j])+1)始终为2，因为仅在j为1时才进行迭代.
• enumerate返回一个元组列表，每个元组都包含索引和值，因此您不需要存储n，并且可以直接针对j进行测试.
• Python可以遍历项目列表，而不必按索引获取它们，这是[list[i]**2 for i in len(list)]和[i**2 for i in list]
之间的区别

• 您不需要在字符串前后加上方括号，因此可以节省一些空间:

• int(n[j])+1) will always be 2, since you are only iterating if j is 1.
• enumerate returns a list of tuples each containing the index and value, so you don't need to store n, and can test against j directly.
• Python can iterate over a list of items without having to fetch them by index, its the difference between [list[i]**2 for i in len(list)] and [i**2 for i in list]

• You don't need to put brackets around the string, so you can save some space by doing this:

" ".join(...)

代替此:

(" ").join(...)

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