【朱迪的LeetCode刷题笔记】151. Reverse Words in a String #Medium #Python #C++

Judie

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 <= 104
s 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?

Judy
Python

1. class Solution(object):
   
2.     def reverseWords(self, s):
   
3.         """
   
4.         :type s: str
   
5.         :rtype: str
   
6.         """
   
7.         lst = s.split(" ")
   
8.         rlst = []
   
9.         l = len(lst)
   
10.         for i in range(l-1,-1,-1):
    
11.             if lst[i] != "":
    
12.                 rlst.append(lst[i])
    
13.         return " ".join(rlst)

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Sol1
Python
https://leetcode.com/problems/re ... code-easy-solution/

1. class Solution(object):
   
2.     def reverseWords(self, s):
   
3.         lst = s.split()
   
4.         lst = lst[::-1]
   
5.         return ' '.join(lst)

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Sol2
Python
https://leetcode.com/problems/re ... /2810978/one-liner/

1. class Solution:
   
2.     def reverseWords(self, s: str) -> str:
   
3.         return ' '.join(reversed(s.split()))

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Mike
C++

1. tring reverseWords(string s) {
   
2.         string reverse = "";
   
3.         string word = "";
   
4.         for (int i = s.size() - 1; i >= 0; i--) {
   
5.             if (s[i] != ' ') {
   
6.                 word = s[i] + word;
   
7.             } else {
   
8.                 if (word.size() > 0) {
   
9.                     reverse += word + " ";
   
10.                     word = "";
    
11.                 }
    
12.             }
    
13.         }
    
14.         if (word.size() > 0) {
    
15.             reverse += word;
    
16.         }
    
17.         if (reverse[reverse.size() - 1] == ' ') {
    
18.             reverse.pop_back();
    
19.         }
    
20.         return reverse;
    
21.     }

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