49. Group Anagrams

Given an array of strings, group anagrams together.
For example, given: [“eat”, “tea”, “tan”, “ate”, “nat”, “bat”],
Return:
[
[“ate”, “eat”,”tea”],
[“nat”,”tan”],
[“bat”]
]

public class Solution {    public List<List<String>> groupAnagrams(String[] strs) {        List<List<String>> rst = new ArrayList<List<String>>();        if(strs == null || strs.length == 0) return rst;        HashMap<String, ArrayList<String>> map = new HashMap<String, ArrayList<String>>();        for(int i = 0; i < strs.length; i++){            String str = strs[i];            int[] count = new int[26];            for(int j = 0; j < str.length(); j++){                char ch = str.charAt(j);                count[ch-'a']++;            }            String key = Arrays.toString(count);            if(!map.containsKey(key)){                map.put(key, new ArrayList<String>());            }            map.get(key).add(str);        }        for(ArrayList<String> al : map.values()){            rst.add(al);        }        return rst;    }}