lc-49

//Given an array of strings strs, group the anagrams together. You can return th
//e answer in any order. 
//
// An Anagram is a word or phrase formed by rearranging the letters of a differe
//nt 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"]]
// 
// 
// Constraints: 
//
// 
// 1 <= strs.length <= 104 
// 0 <= strs[i].length <= 100 
// strs[i] consists of lowercase English letters. 
// 
// Related Topics Array Hash Table String Sorting 
// 👍 10416 👎 338


//leetcode submit region begin(Prohibit modification and deletion)
class Solution {
    public List<List<String>> groupAnagrams(String[] strs) {
        Map<String, List<String>> resultMap = new HashMap<>();

        for (String str : strs) {
            String key = generateKey(str);
            resultMap.putIfAbsent(key, new ArrayList<>());
            resultMap.get(key).add(str);
        }

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

    private String generateKey(String str) {
        int[] nums = new int[26];

        for (char ch : str.toCharArray()) {
            nums[ch - 'a']++;
        }

        StringBuilder stringBuilder = new StringBuilder();
        for (int i = 0; i < 26; i++) {
            stringBuilder.append('a' + i).append(nums[i]);
        }

        return stringBuilder.toString();
    }
}
//leetcode submit region end(Prohibit modification and deletion)