Leetcode: Group Anagrams

 

Given an array of strings, group anagrams together.

Example:

Input: ["eat", "tea", "tan", "ate", "nat", "bat"],
Output:
[
  ["ate","eat","tea"],
  ["nat","tan"],
  ["bat"]
]
Note:

All inputs will be in lowercase.
The order of your output does not matter.

if want lexicographic order，然后要用Collections.sort() 来保证字典序

for (List<String> each : map.values()) {
　　Collections.sort(each);
　　res.add(new ArrayList<String>(each));
}

class Solution {
    public List<List<String>> groupAnagrams(String[] strs) {
        List<List<String>> res = new ArrayList<>();
        HashMap<String, List<String>> map = new HashMap<>();
        
        for (String str : strs) {
            char[] arr = str.toCharArray();
            Arrays.sort(arr);
            String sorted = Arrays.toString(arr);
            // if (!map.containsKey(sorted)) map.put(sorted, new ArrayList<String>());
            map.putIfAbsent(sorted, new ArrayList<String>());
            map.get(sorted).add(str);
        }
        
        for (List<String> value : map.values()) {
            res.add(value);
        }
        return res;
    }
}