0567. Permutation in String

# 567. Permutation in String#

## 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.

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

``````

Note:

1. The input strings only contain lower case letters.
2. The length of both given strings is in range [1, 10,000].

## 代码 #

``````
package leetcode

func checkInclusion(s1 string, s2 string) bool {
var freq [256]int
if len(s2) == 0 || len(s2) < len(s1) {
return false
}
for i := 0; i < len(s1); i++ {
freq[s1[i]-'a']++
}
left, right, count := 0, 0, len(s1)

for right < len(s2) {
if freq[s2[right]-'a'] >= 1 {
count--
}
freq[s2[right]-'a']--
right++
if count == 0 {
return true
}
if right-left == len(s1) {
if freq[s2[left]-'a'] >= 0 {
count++
}
freq[s2[left]-'a']++
left++
}
}
return false
}

``````

Apr 8, 2023