0438 Find All Anagrams in a String

0438 Find All Anagrams in a String.java

class Solution {
    public List<Integer> findAnagrams(String s, String p) {
        List<Integer> list = new ArrayList<>();
        if (s == null || s.length() == 0 || p == null || p.length() == 0 || s.length() < p.length()) return list;
        int[] hash = new int[26];
        for (char c : p.toCharArray()) {
            hash[c - 'a']++;
        }
        int left = 0, right = 0, count = p.length();
        while (right < s.length()) {
            if (hash[s.charAt(right++) - 'a']-- >= 1) count--;
            if (count == 0) list.add(left);
            if (right - left == p.length() && hash[s.charAt(left++) - 'a']++ >= 0) count++;
        }
        return list;
    }
}