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

 public class Solution {
     public List<String> anagrams(String[] strs) {
         List<String> ret = new ArrayList<String>();

         if (strs == null) {
             return ret;
         }

         HashMap<String, List<String>> map = new HashMap<String, List<String>>();

         int len = strs.length;
         for (int i = ; i < len; i++) {
             String s = strs[i];

             // Sort the string.
             char[] chars = s.toCharArray();
             Arrays.sort(chars);
             String strSort = new String(chars);   

             // Create a ArrayList for the sorted string.
             if (!map.containsKey(strSort)) {
                 map.put(strSort, new ArrayList<String>());
             }

             // Add a new string to the list of the hashmap.
             map.get(strSort).add(s);
         }

         // go through the map and add all the strings into the result.
         for (Map.Entry<String, List<String>> entry: map.entrySet()) {
             List<String> list = entry.getValue();

             // skip the entries which only have one string.
             if (list.size() == ) {
                 continue;
             }

             // add the strings into the list.
             ret.addAll(list);
         }

         return ret;
     }
 }

2015.1.3 redo:

 public class Solution {
     public List<String> anagrams(String[] strs) {
         List<String> ret = new ArrayList<String>();
         if (strs == null) {
             return ret;
         }

         HashMap<String, List<String>> map = new HashMap<String, List<String>>();
         for (int i = 0; i < strs.length; i++) {
             String s = strs[i];
             char[] chars = s.toCharArray();

             Arrays.sort(chars);
             String sSort = new String(chars);

             if (map.containsKey(sSort)) {
                 map.get(sSort).add(s);
             } else {
                 List<String> list = new ArrayList<String>();
                 list.add(s);
                 map.put(sSort, list);
             }
         }

         // Bug 1: should use map.entrySet() instead of MAP.
         for (Map.Entry<String, List<String>> entry: map.entrySet()) {
             List<String> list = entry.getValue();
             if (list.size() > 1) {
                 ret.addAll(list);
             }
         }

         return ret;
     }
 }

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