Leetcode_567.java

public class Leetcode_567 {
 public boolean checkInclusion(String s1, String s2) {
 int[] freq1 = new int[26];
 int[] freq2 = new int[26];
 int n1 = s1.length();
 int n2 = s2.length();
 int l = 0, r = n1;

 if (n2 < n1) return false;

 for (int i = 0; i < n1; i++) {
 freq1[s1.charAt(i) - 'a']++;
 freq2[s2.charAt(i) - 'a']++;
 }
 while (r <= n2) {
 if (isMatching(freq1, freq2)) return true;
 freq2[s2.charAt(l) - 'a']--;
 if (r < n2)
 freq2[s2.charAt(r) - 'a']++;
 l++;
 r++;
 }
 return false;
 }
 private boolean isMatching(int[] freq1, int[] freq2) {
 for (int i = 0; i < 26; i++) {
 if (freq1[i] != freq2[i]) return false;
 }
 return true;
 }
 public static void main(String[] args) {
 Leetcode_567 obj = new Leetcode_567();
 System.out.println(obj.checkInclusion("ab", "eidbaooo"));
 }
}