49-group-anagrams.java

/*
49. Group Anagrams
Medium - 71.6%

Given an array of strings strs, group the anagrams together. You can return the answer in any order.

An Anagram is a word or phrase formed by rearranging the letters of a different word or phrase, 
typically using all the original letters exactly once.

Example 1:
Input: strs = ["eat","tea","tan","ate","nat","bat"]
Output: [["bat"],["nat","tan"],["ate","eat","tea"]]

Example 2:
Input: strs = [""]
Output: [[""]]

Example 3:
Input: strs = ["a"]
Output: [["a"]]
*/

import java.util.*;

class Solution {
    public List<List<String>> groupAnagrams(String[] strs) {
        Map<String, List<String>> groups = new HashMap<>();
        
        for (String str : strs) {
            // Create a key by sorting the characters
            char[] chars = str.toCharArray();
            Arrays.sort(chars);
            String key = new String(chars);
            
            // Group strings with the same sorted key
            groups.computeIfAbsent(key, k -> new ArrayList<>()).add(str);
        }
        
        // Extract all groups
        return new ArrayList<>(groups.values());
    }
}