[LeetCode] 567. Permutation in String

Problem

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:

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

Solution

class Solution {
    public boolean checkInclusion(String s1, String s2) {
        int l1 = s1.length(), l2 = s2.length();
        if (l2 < l1) return false;
        
        Map<Character, Integer> map = new HashMap<>();
        for (int i = 0; i < l1; i++) {
            map.put(s1.charAt(i), map.getOrDefault(s1.charAt(i), 0)+1);
            map.put(s2.charAt(i), map.getOrDefault(s2.charAt(i), 0)-1);
        }
        if (checkMap(map)) return true;
        for (int i = l1; i < l2; i++) {
            map.put(s2.charAt(i), map.getOrDefault(s2.charAt(i), 0)-1);
            map.put(s2.charAt(i-l1), map.get(s2.charAt(i-l1))+1);
            if (checkMap(map)) return true;
        }
        return false;
    }
    private boolean checkMap(Map<Character, Integer> map) {
        for (Map.Entry<Character, Integer> entry: map.entrySet()) {
            if (entry.getValue() != 0) return false;
        }
        return true;
    }
}

using int array as map

class Solution {
    public boolean checkInclusion(String s1, String s2) {
        if (s1 == null || s2 == null || s1.length() > s2.length()) return false;
        int[] count = new int[26];
        for (int i = 0; i < s1.length(); i++) {
            count[s1.charAt(i)-'a']++;
            count[s2.charAt(i)-'a']--;
        }
        if (allZero(count)) return true;
        for (int i = s1.length(); i < s2.length(); i++) {
            count[s2.charAt(i)-'a']--;
            count[s2.charAt(i-s1.length())-'a']++;
            if (allZero(count)) return true;
        }
        return false;
    }
    
    private boolean allZero(int[] arr) {
        for (int i: arr) {
            if (i != 0) return false;
        }
        return true;
    }
}