python實現字符串的倒序（五種）

今天看到一個面試題，說實現一串字符串的倒序。如：“abcde" --> "edcba"

 

1. 使用python的特性

   s = "abcde"
   
   def str_reverse1(s):
   
       return s[::-1]
   
   if __name__ == '__main__':
       rs = str_reverse1(s)
       print(rs)

    

2. 使用列表

   s = "abcde"
   
   def str_reverse2(s):
       # l = list(s).reverse()     #錯誤
       l = list(s)
       l.reverse()
       return "".join(l)
   
   if __name__ == '__main__':
       rs = str_reverse2(s)
       print(rs)

    

3. 使用循環

   s = "abcde"
   
   def str_reverse3(s):
       s1 = ""
       for s2 in s[::-1]:
           s1 += s2
   
       return s1
   
   if __name__ == '__main__':
       rs = str_reverse3(s)
       print(rs)

    

4. 使用庫collections

   from collections import deque
   s = "abcde"
   
   def str_reverse4(s):
       dq = deque(s)       # or      dq = deque()
       dq.reverse()        #         dq.extendleft(s)
       return "".join(dq)
   
   if __name__ == '__main__':
       rs = str_reverse4(s)
       print(rs)

    

5. 使用遞歸

   s = "abcde"
   
   def str_reverse5(s):
   
       if len(s) <= 1:
           return s
   
       return str_reverse5(s[1:])+s[0]
   
   if __name__ == '__main__':
       rs = str_reverse5(s)
       print(rs)