Group Anagrams leetcode

Given an array of strings, return all groups of strings that are anagrams.

Note: All inputs will be in lower-case.

把给的string都变成charArray然后排序, 把sort好的再变成string 存入hashmap, map 的value值为一个list<> list内存放变形之前的string.

如果一个string在hashmap中出现过 这个string一定是个变形词 把各个string放入对应的list中,遍历一次时间复杂度O(nlogn) + O(n*klogk) = O(nlogn)

public class Solution {
    public List<List<String>> groupAnagrams(String[] strs) {
        List<List<String>> res = new ArrayList<List<String>>();
        if (strs == null || strs.length == 0) {
            return res;
        }
        Arrays.sort(strs);
        HashMap<String, List<String>> map = new HashMap<String, List<String>>();
        for (String s : strs) {
            char[] chararray = s.toCharArray();
            Arrays.sort(chararray);
            String temstr = new String(chararray);
            if (map.containsKey(temstr)) {
                map.get(temstr).add(s);
            } else {
                List<String> tem = new ArrayList<String>();
                tem.add(s);
                map.put(temstr, tem);
            }
        }
        for (List<String> l : map.values()) {
            res.add(l);
        }
        return res;
    }
}