leetcode-49 Group Anagrams 同位词字典序排序

问题描述：

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

Return:

[
  ["ate","eat","tea"],
 ["nat","tan"],
  ["bat"]
]

Note:
For the return value, each inner list's elements must follow the lexicographic order.

All inputs will be in lower-case.
Update (2015-08-09):

The signature of the function had been updated to return List<List<String>> insteadof List<String>, as suggested here.
If you still see your function signature return a List<String>,please click the reload button  to reset your code definition.
 

问题分析：

字典序排序的方法有很多，这里图方便利用了集合中的sort方法进行排序。

查找匹配问题最好使用HashMap；

 

代码：

public class Solution {
public List<List<String>> groupAnagrams(String[] strs) {
List<List<String>>result = new ArrayList<>();
if(strs == null || strs.length == 0)
return result;
//将字典序的字符串作为key，将其同位词组转到一个List中存储到HashMap中
HashMap<String,List<String>>map = new HashMap<>();

for(int i = 0; i < strs.length; i++) {
char[] chars = strs[i].toCharArray();
// 字典序排序
Arrays.sort(chars);
String temp = new String(chars);

if (!map.containsKey(temp)) {
List<String> result_list = new ArrayList<>();
result_list.add(strs[i]);
map.put(temp, result_list);
} else {
map.get(temp).add(strs[i]);
}
}

//遍历map，对ArrayList进行字典序排序
Iterator<Map.Entry<String,List<String>>>iterator = map.entrySet().iterator();
while(iterator.hasNext()) {
Map.Entry<String,List<String>> entry = iterator.next();
List<String> temp_list = entry.getValue();
Collections.sort(temp_list);
result.add(temp_list);
}
return result;
}
}