Update 0151.翻转字符串里的单词.md

problems/0151.翻转字符串里的单词.md

@@ -434,134 +434,40 @@ class Solution {
 ```
 
 python:
-
+（版本一）先删除空白，然后整个反转，最后单词反转。
+### 因为字符串是不可变类型，所以反转单词的时候，需要将其转换成列表，然后通过join函数再将其转换成列表，所以空间复杂度不是O(1)
 ```Python
 class Solution:
-  #1.去除多余的空格
-        def trim_spaces(self, s):     
-            n = len(s)
-            left = 0
-            right = n-1
-        
-            while left <= right and s[left] == ' ':    #去除开头的空格
-                left += 1
-            while left <= right and s[right] == ' ':   #去除结尾的空格
-                right -= 1
-            tmp = []
-            while left <= right:                      #去除单词中间多余的空格
-                if s[left] != ' ':
-                    tmp.append(s[left])
-                elif tmp[-1] != ' ':                 #当前位置是空格，但是相邻的上一个位置不是空格，则该空格是合理的
-                    tmp.append(s[left])
-                left += 1
-            return tmp
-	    
- #2.翻转字符数组
-        def reverse_string(self, nums, left, right):
-            while left < right:
-                nums[left], nums[right] = nums[right], nums[left]
-                left += 1
-                right -= 1
-            return None
-	    
- #3.翻转每个单词
-        def reverse_each_word(self, nums):
-            start = 0
-            end = 0
-            n = len(nums)
-            while start < n:
-                while end < n and nums[end] != ' ':
-                    end += 1
-                self.reverse_string(nums, start, end-1)
-                start = end + 1
-                end += 1
-            return None
-
-#4.翻转字符串里的单词
-        def reverseWords(self, s):                #测试用例："the sky is blue"
-            l = self.trim_spaces(s)               #输出：['t', 'h', 'e', ' ', 's', 'k', 'y', ' ', 'i', 's', ' ', 'b', 'l', 'u', 'e'
-            self.reverse_string(l,  0, len(l)-1)  #输出：['e', 'u', 'l', 'b', ' ', 's', 'i', ' ', 'y', 'k', 's', ' ', 'e', 'h', 't']
-            self.reverse_each_word(l)             #输出：['b', 'l', 'u', 'e', ' ', 'i', 's', ' ', 's', 'k', 'y', ' ', 't', 'h', 'e']
-            return ''.join(l)                    #输出：blue is sky the
-
+    def reverseWords(self, s: str) -> str:
+        # 删除前后空白
+        s = s.strip()
+        # 反转整个字符串
+        s = s[::-1]
+        # 将字符串拆分为单词，并反转每个单词
+        s = ' '.join(word[::-1] for word in s.split())
+        return s
 
 ```
+（版本二）使用双指针
 
 ```python
 class Solution:
     def reverseWords(self, s: str) -> str:
-        # method 1 - Rude but work & efficient method.
-        s_list = [i for i in s.split(" ") if len(i) > 0]
-        return " ".join(s_list[::-1])
+        # 将字符串拆分为单词，即转换成列表类型
+        words = s.split()
 
-        # method 2 - Carlo's idea
-        def trim_head_tail_space(ss: str):
-            p = 0
-            while p < len(ss) and ss[p] == " ":
-                p += 1
-            return ss[p:]
+        # 反转单词
+        left, right = 0, len(words) - 1
+        while left < right:
+            words[left], words[right] = words[right], words[left]
+            left += 1
+            right -= 1
 
-        # Trim the head and tail space
-        s = trim_head_tail_space(s)
-        s = trim_head_tail_space(s[::-1])[::-1]
-
-        pf, ps, s = 0, 0, s[::-1] # Reverse the string.
-        while pf < len(s):
-            if s[pf] == " ":
-                # Will not excede. Because we have clean the tail space.
-                if s[pf] == s[pf + 1]:
-                    s = s[:pf] + s[pf + 1:]
-                    continue
-                else:
-                    s = s[:ps] + s[ps: pf][::-1] + s[pf:]
-                    ps, pf = pf + 1, pf + 2
-            else:
-                pf += 1
-        return s[:ps] + s[ps:][::-1] # Must do the last step, because the last word is omit though the pointers are on the correct positions,
+        # 将列表转换成字符串
+        return " ".join(words)
 ```
 
-```python
-class Solution: # 使用双指针法移除空格
-    def reverseWords(self, s: str) -> str:
-        
-        def removeextraspace(s):
-            start = 0; end = len(s)-1
-            while s[start]==' ':
-                start+=1
-            while s[end]==' ':
-                end-=1
-            news = list(s[start:end+1])
-            slow = fast = 0
-            while fast<len(news):
-                while fast>0 and news[fast]==news[fast-1]==' ':
-                    fast+=1
-                news[slow]=news[fast]
-                slow+=1; fast+=1
-            #return "".join(news[:slow])
-            return news[:slow]
 
-        def reversestr(s):
-            left,right = 0,len(s)-1
-            news = list(s)
-            while left<right:
-                news[left],news[right] = news[right],news[left]
-                left+=1; right-=1
-            #return "".join(news)
-            return news
-
-        news = removeextraspace(s)
-        news.append(' ')
-        fast=slow=0
-        #print(news)
-        while fast<len(news):
-            while news[fast]!=' ':
-                fast+=1
-            news[slow:fast] = reversestr(news[slow:fast])
-        #    print(news[slow:fast])
-            fast=slow=fast+1
-        news2 = reversestr(news[:-1])
-        return ''.join(news2)
-```
 Go：
 
 ```go