import java.util.ArrayList;
import java.util.List;

public class Solution {
 /**
 * @param s a string
 * @param p a non-empty string
 * @return a list of index
 */
 public List<Integer> findAnagrams(String s, String p) {
 // Write your code here
 	ArrayList<Integer> list = new ArrayList<>();
 	int lenS = s.length(), lenP = p.length();
 	if (lenS < lenP) {
 		return list;
 	}
 	int[] cntS = new int[26];
 	int[] cntP = new int[26];
 	for (int i=0; i<lenP; ++i) {
 		++cntP[p.charAt(i) - 'a'];
 		++cntS[s.charAt(i) - 'a'];
 	}
 	if (check(cntS, cntP) == true) {
 		list.add(0);
 	}
 	for (int i=1; i<=lenS-lenP; ++i) {
 		--cntS[s.charAt(i-1) - 'a'];
 		++cntS[s.charAt(i-1+lenP) - 'a'];
 		if (check(cntS, cntP) == true) {
 			list.add(i);
 		}
 	}
 	return list;
 }
 private boolean check(int[] cntS, int[] cntP) {
 	for (int i=0; i<26; ++i) {
 		if (cntS[i] != cntP[i]) {
 			return false;
 		}
 	}
 	return true;
 }
}