151-reverse-words-in-a-string
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.
My solution：
```python class Solution(object): def reverseWords(self, s): “”” :type s: str :rtype: str “”” s = s.strip() arr = [] i,j = 0,0 while j < len(s): while j < len(s) and s[j] != ‘ ‘: j += 1 arr.append(s[i:j]) while j < len(s) and s[j] == ‘ ‘ : j += 1 i = j
1
return ' '.join(arr[::-1])
Time Complexity: O(n) Space Complexity: O(1)