Group Anagrams – LeetCode Solution Java , Python 3, Python 2 , C , C++, Best and Optimal Solutions , All you need.

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"]]

Constraints:

• 1 <= strs.length <= 104
• 0 <= strs[i].length <= 100
• strs[i] consists of lowercase English letters.

C++ Group Anagrams LeetCode Solution

class Solution {
public:
    vector<vector<string>> groupAnagrams(vector<string>& strs) {
        // Base case
		if(strs.size() == 1)
            return {{strs[0]}};
        
        vector<vector<string>> ans;
        unordered_map<string, vector<string>> M;
        for(int  i = 0; i < strs.size(); i++)
        {
            string str = strs[i];
            sort(strs[i].begin(), strs[i].end()); // Sorting the string
            M[strs[i]].push_back(str);  // Sorted string is the key and the value is the initial string
        }
        for(auto i = M.begin(); i != M.end(); i++)
            ans.push_back(i -> second);  // Traversing the map and adding the vectors of string to ans
        return ans;
    }
};

Java Group Anagrams LeetCode Solution

   public List<List<String>> groupAnagrams(String[] strs) {
        if (strs == null || strs.length == 0) return new ArrayList<>();
        Map<String, List<String>> map = new HashMap<>();
        for (String s : strs) {
            char[] ca = new char[26];
            for (char c : s.toCharArray()) ca[c - 'a']++;
            String keyStr = String.valueOf(ca);
            if (!map.containsKey(keyStr)) map.put(keyStr, new ArrayList<>());
            map.get(keyStr).add(s);
        }
        return new ArrayList<>(map.values());
    }
 

Python 3 Group Anagrams LeetCode Solution

from collections import defaultdict

class Solution:
    def groupAnagrams(self, strs: List[str]) -> List[List[str]]:
        letters_to_words = defaultdict(list)
        for word in strs:
            letters_to_words[tuple(sorted(word))].append(word)
        return list(letters_to_words.values())

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