Given two strings s1 and s2, write a function to return true if s2 contains the permutation of s1. In other words, one of the first string’s permutations is the substring of the second string.
Example 1:
Input: s1 = "ab" s2 = "eidbaooo"
Output: True
Explanation: s2 contains one permutation of s1 ("ba").
Example 2:
Input:s1= "ab" s2 = "eidboaoo"
Output: False
Solution
这个题和438题几乎一模一样，我们还是用来做，如果s2的子串是s1的排列，那么他们对应的Counter应该是一样的。 同样使用活动窗口的思路。
class Solution:
def checkInclusion(self, s1: str, s2: str) -> bool:
cp = Counter(s1)
lp =len(s1)
i = 0
sc= Counter(s2[i:i+ lp-1])
while (i+lp<=len(s2)):
sc[s2[i+lp -1]] +=1
if sc ==cp:
return True
sc[s2[i]] -=1
if sc[s2[i]] ==0:
del sc[s2[i]]
i = i+1
return False
