Count words in a sentence

Count the words in a given sentence, handling extra spaces and empty input.

strings split counting

Write a function `count_words(sentence)` that takes a string `sentence` and returns the number of words in it. A word is defined as a maximal sequence of non-whitespace characters. For example, the sentence "Hello world" has 2 words. The sentence may contain leading, trailing, or multiple spaces between words; these should be ignored. If the sentence is empty or contains only whitespace, the function should return 0.

Constraints

The input string `sentence` can be any Python string, including empty. Its length is at most 10^5 characters. The function should run in O(n) time and O(n) space, where n is the length of the input.

Example

>>> count_words("Hello world")
2
>>> count_words("   This   is   a   test.   ")
4
>>> count_words("")
0
>>> count_words("   ")
0

10 points ~10 min

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Hints

Consider using the built-in string method `split()` without arguments, which splits on any whitespace and handles multiple spaces automatically.

The `split()` method returns a list of words, so the answer is just the length of that list.

For an empty string or whitespace-only string, `split()` returns an empty list, so its length is 0.

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