Find All Anagrams in a String

1package pkg5leetcode.interview150;2 3/*4 * Find All Anagrams in a String | LC 4385 * APPROACH: Sliding window with char frequency match count.6 * COMPLEXITY: Time O(n), Space O(1)7 */8import java.util.*;9 10public class interview150_LC438FindAllAnagramsInAString {11    static List<Integer> findAnagrams(String s, String p) {12        List<Integer> res = new ArrayList<>();13        if (p.length() > s.length()) return res;14        int[] need = new int[26], have = new int[26];15        for (char c : p.toCharArray()) need[c - 'a']++;16        for (int i = 0; i < s.length(); i++) {17            have[s.charAt(i) - 'a']++;18            if (i >= p.length()) have[s.charAt(i - p.length()) - 'a']--;19            if (i >= p.length() - 1 && Arrays.equals(need, have)) res.add(i - p.length() + 1);20        }21        return res;22    }23 24    public static void main(String[] args) {25        check(findAnagrams("cbaebabacd", "abc").equals(Arrays.asList(0, 6)), "case1");26        check(findAnagrams("abab", "ab").equals(Arrays.asList(0, 1, 2)), "case2");27        System.out.println("all tests passed");28    }29 30    static void check(boolean cond, String name) {31        if (!cond) throw new AssertionError("FAILED: " + name);32        System.out.println("  PASS " + name);33    }34}