Given an input string s, reverse the order of the words.A word is defined as a sequence of non-space characters. The words in s will be separated by at least one space.Return a string of the words in reverse order concatenated by a single space.Note that s may contain leading or trailing spaces or multiple spaces between two words. The returned string should only have a single space separating the words. Do not include any extra spaces. Example 1:Input: s = "the sky is blue"Output: "blue is sky the"Example 2:Input: s = " hello world "Output: "world hello"Explanation: Your reversed string should not contain leading or trailing spaces.Example 3:Input: s = "a good example"Output: "example good a"Explanation: You need to reduce multiple spaces between two words to a single space in the reversed string. Constraints:1 <= s.length <= 104s contains English letters (upper-case and lower-case), digits, and spaces ' '.There is at least one word in s. Follow-up: If the string data type is mutable in your language, can you solve it in-place with O(1) extra space?
Question
Given an input string s, reverse the order of the words.A word is defined as a sequence of non-space characters. The words in s will be separated by at least one space.Return a string of the words in reverse order concatenated by a single space.Note that s may contain leading or trailing spaces or multiple spaces between two words. The returned string should only have a single space separating the words. Do not include any extra spaces. Example 1:Input: s = "the sky is blue"Output: "blue is sky the"Example 2:Input: s = " hello world "Output: "world hello"Explanation: Your reversed string should not contain leading or trailing spaces.Example 3:Input: s = "a good example"Output: "example good a"Explanation: You need to reduce multiple spaces between two words to a single space in the reversed string. Constraints:1 <= s.length <= 104s contains English letters (upper-case and lower-case), digits, and spaces ' '.There is at least one word in s. Follow-up: If the string data type is mutable in your language, can you solve it in-place with O(1) extra space?
Solution
Sure, here is a step-by-step solution in Python:
- First, we need to split the string into words. In Python, we can use the
split()function which splits a string into a list where each word is a list item. By default,split()divides a string into words using space as the separator. However, it also removes leading, trailing and multiple spaces between words. Here is how to do it:
words = s.split()
- Next, we need to reverse the order of the words. In Python, we can use the
reverse()function which reverses the order of elements in a list:
words.reverse()
- Finally, we need to join the words back into a string with a single space between each word. In Python, we can use the
join()function which concatenates all the elements in a list into a string with a specified delimiter:
reversed_s = ' '.join(words)
- So, the complete solution is:
def reverseWords(s):
words = s.split()
words.reverse()
return ' '.join(words)
This solution works in O(n) time where n is the length of the string, and it uses O(n) extra space to store the words. If the string data type is mutable in your language and you need to solve it in-place with O(1) extra space, you would need a more complex algorithm that reverses the string word by word directly in the input string. However, Python's string data type is immutable, so this is not possible in Python.
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