Group Anagrams - LeetCode

// Group Anagrams - https://leetcode.com/problems/group-anagrams/

class Solution {

    // Using HashMap to build dictionary
    // Time Complexity: O(n * klogk)
    //  where k is the length of string
    // Space Complexity: O(n * k)

    // Key Clarifications
    // - Do we need special handling for empty strings
    // - Can we assume that input strings are all lowercase
    // public List<List<String>> groupAnagrams(String[] strs) {

    //     Map<String, List<String>> map = new HashMap<>();

    //     for(int i = 0; i < strs.length; i++) {
    //         char[] charArray = strs[i].toCharArray();
    //         Arrays.sort(charArray);
    //         String sorted = new String(charArray);

    //         List<String> anagrams = map.getOrDefault(sorted, new ArrayList<>());
    //         anagrams.add(strs[i]);
    //         map.put(sorted, anagrams);
    //     }

    //     List<List<String>> result = new ArrayList<>();
    //     for(List<String> anagrams: map.values()) {
    //         result.add(anagrams);
    //     }

    //     return result;
    // }

    // Same as above but compact code
    public List<List<String>> groupAnagrams(String[] strs) {

        Map<String, List<String>> map = new HashMap<>();
        for(int i = 0; i < strs.length; i++) {
            char[] charArray = strs[i].toCharArray();
            Arrays.sort(charArray);
            String sorted = new String(charArray);
            map.putIfAbsent(sorted, new ArrayList<>());
            map.get(sorted).add(strs[i]);
        }

        return new ArrayList<>(map.values());
    }
}