LeetCode----Word Pattern

LeetCode----Word Pattern

Word Pattern

Given a pattern and a string str, find if str follows the same pattern.

Here follow means a full match, such that there is a bijection between a letter in pattern and a non-empty word in str.

Examples:

1. pattern = abba, str = dog cat cat dog should return true.
2. pattern = abba, str = dog cat cat fish should return false.
3. pattern = aaaa, str = dog cat cat dog should return false.
4. pattern = abba, str = dog dog dog dog should return false.

    

   Notes:
   You may assume pattern contains only lowercase letters, and str contains lowercase letters separated by a single space.

   
   

   分析：

   按模式匹配給定字符串。

   我的做法是，先講模式如“aabb”，構造成模式字典pd＝{'a':None, 'b':None}。再將給定串如“dog dog cat cat”按空格切分。然後，按順序去對應串和字典中鍵，如果不匹配則不符合該模式。最後，再判斷字典中不同鍵值對應的串是否相同，如果相同，也不符合該模式。

    

   代碼：

    

   class Solution(object):
       def wordPattern(self, pattern, str):
           
           :type pattern: str
           :type str: str
           :rtype: bool
           
           pd = dict(map(lambda a: (a, None), list(pattern)))
           slst = str.split()
           if len(pattern) != len(slst):
               return False
           for i in range(len(slst)):
               if pd[pattern[i]] is None:
                   pd[pattern[i]] = slst[i]
               else:
                   if pd[pattern[i]] != slst[i]:
                       return False
           s = set()
           for i in pd:
               s.add(pd[i])
           if len(s) != len(pd):
               return False
           return True