0567 - Permutation in String

0567 - Permutation in String

Given two strings s1 and s2, return true if s2 contains a permutation of s1, or false otherwise.

In other words, return true if one of s1's permutations is the substring of s2.

Examples

Input: s1 = "ab", s2 = "eidbaooo" Output: true Explanation: s2 contains one permutation of s1 ("ba").

Input: s1 = "ab", s2 = "eidboaoo" Output: false

Constraints

1 <= s1.length, s2.length <= 104 s1 and s2 consist of lowercase English letters.

Java Solution

class Solution {
    public boolean checkInclusion(String s1, String s2) {
        if (s1.length() > s2.length()) return false;
        int[] s1map = new int[26];
        int[] s2map = new int[26];
        
        for(int i = 0; i < s1.length(); i++) {
            s1map[s1.charAt(i) - 'a']++;
            s2map[s2.charAt(i) - 'a']++;
        }
        
        for (int i = 0; i < s2.length() - s1.length(); i++) {
            if (matches(s1map, s2map))
                return true;
            s2map[s2.charAt(i + s1.length()) - 'a']++;
            s2map[s2.charAt(i) - 'a']--;
        }
        return matches(s1map, s2map);
    }
    
    public boolean matches(int[] s1map, int[] s2map) {
        for (int i = 0; i < 26; i++) {
            if (s1map[i] != s2map[i])
                return false;
        }
        return true;
    }
}