leetcode438 -- find all anagrams in a string

leetcode438 -- find all anagrams in a string

题目

Given a string s and a non-empty string p, find all the start indices of p's anagrams in s.

Strings consists of lowercase English letters only and the length of both strings s and p will not be larger than 20,100.

The order of output does not matter.

Example 1:

Input:
s: "cbaebabacd" p: "abc"

Output:
[0, 6]

Explanation:
The substring with start index = 0 is "cba", which is an anagram of "abc".
The substring with start index = 6 is "bac", which is an anagram of "abc".

这个题目的意思是找到所有的字符串与是给定的字符串的一个换位。

方法是用p建立一个数组或者是一个字典,然后每次取这么长的与建立的数组或者字典进行比较。

class Solution(object):
    def findAnagrams(self, s, p):
        """
        :type s: str
        :type p: str
        :rtype: List[int]
        """
        
        temp = self.helper(p)
        res = []
        for i in range(0,len(s)-len(p)+1):
            ss = s[i:len(p)+i]
            if self.helper(ss)==temp:
                res.append(i)
        return res
    
    
    def helper(self, ss):
        dic = [0]*26
        for i in range(len(ss)):
            dic[ord(ss[i])-ord('a')] += 1
        return dic
       

a代表97, z代表122

但是像上面写的话,每一次都要建立一个长的数组有些花时,只有第一次需要建立一个,后面的其实并不需要。

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