LeetCode:Group Anagrams

Group Anagrams

Total Accepted: 76941  Total Submissions: 275801  Difficulty: Medium

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:

1. For the return value, each inner list's elements must follow the lexicographic order.
2. All inputs will be in lower-case.

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  (E) Valid Anagram (E) Group Shifted Strings

思路：

使用先将字符串数组排序（这样可以保证输出的顺序）；

使用HashMap<String, List<String>>，key(String)：是第一次出现的字符串；value(List<String>)：用于保存所有相同字母乱序的值。

java code:

public class Solution {
    public List<List<String>> groupAnagrams(String[] strs) {
        
        if(strs==null || strs.length==0) return new ArrayList<List<String>>();
        
        Map<String, List<String>> map = new HashMap<String, List<String>>();
        Arrays.sort(strs);
        
        for(String str : strs) {
            char[] cs = str.toCharArray();
            Arrays.sort(cs);
            String keyStr = new String(cs);
            
            if(!map.containsKey(keyStr)) map.put(keyStr, new ArrayList<String>());
            map.get(keyStr).add(str);
        }
        
        return new ArrayList<List<String>>(map.values());
    }
}