LeetCode: Anagrams 解题报告

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

Note: All inputs will be in lower-case.

思路：

建Hashtable，用排序过的string作为key，它的anagram作为ArrayList

这道题之前用暴力写的O(N^2)的TLE了，改用Hashtable来写
题目的意思是给一个String数组，找出其中由相同字母组成的单词。
例如：
S = ["abc", "bca", "bac", "bbb", "bbca", "abcb"]
答案为：
["abc", "bca", "bac", "bbca", "abcb"]
只有"bbb"没有相同字母组成的单词。

ref: http://blog.csdn.net/fightforyourdream/article/details/14217985

 1 public class Solution {
 2     public List<String> anagrams(String[] strs) {
 3         List<String> ret = new ArrayList<String>();
 4
 5         if (strs == null) {
 6             return ret;
 7         }
 8
 9         HashMap<String, List<String>> map = new HashMap<String, List<String>>();
10
11         int len = strs.length;
12         for (int i = 0; i < len; i++) {
13             String s = strs[i];
14
15             // Sort the string.
16             char[] chars = s.toCharArray();
17             Arrays.sort(chars);
18             String strSort = new String(chars);
19
20             // Create a ArrayList for the sorted string.
21             if (!map.containsKey(strSort)) {
22                 map.put(strSort, new ArrayList<String>());
23             }
24
25             // Add a new string to the list of the hashmap.
26             map.get(strSort).add(s);
27         }
28
29         // go through the map and add all the strings into the result.
30         for (Map.Entry<String, List<String>> entry: map.entrySet()) {
31             List<String> list = entry.getValue();
32
33             // skip the entries which only have one string.
34             if (list.size() == 1) {
35                 continue;
36             }
37
38             // add the strings into the list.
39             ret.addAll(list);
40         }
41
42         return ret;
43     }
44 }

https://github.com/yuzhangcmu/LeetCode_algorithm/blob/master/hash/Anagrams.java