题目
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.
解题思路
用sliding window扫描s2，把字符串放到一个计数器中，每次更新这个计数器并和p的计数器比较，如果相同就返回True
代码
class Solution:
def checkInclusion(self, p: str, s: str) -> bool:
def f(c):
return ord(c) - 97
ct_s, ct_p = [0] * 26, [0] * 26
for c in p:
ct_p[f(c)] += 1
l = len(p)
for c in s[: l - 1]:
ct_s[f(c)] += 1
for i, c in enumerate(s[l - 1:]):
ct_s[f(c)] += 1
if ct_s == ct_p:
return True
ct_s[f(s[i])] -= 1
return False
