[Leetcode] Anagrams

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

Note: All inputs will be in lower-case.

这题先得知道啥叫Anagrams，知道后其实很简单。

首先简单介绍一下Anagram（回文构词法）。Anagrams是指由颠倒字母顺序组成的单词，比如“dormitory”颠倒字母顺序会变成“dirty room”，“tea”会变成“eat”。

回文构词法有一个特点：单词里的字母的种类和数目没有改变，只是改变了字母的排列顺序。

For example:

Input:　　["tea","and","ate","eat","den"]

Output:   ["tea","ate","eat"]

 1 class Solution {

 2 public:

 3     vector<string> anagrams(vector<string> &strs) {

 4         string s;

 5         map<string, int> anagram;

 6         vector<string> res;

 7         for (int i = 0; i < strs.size(); ++i) {

 8             s = strs[i];

 9             sort(s.begin(), s.end());

10             if (anagram.find(s) == anagram.end()) {

11                 anagram[s] = i;

12             } else {

13                 if (anagram[s] >= 0) {

14                     res.push_back(strs[anagram[s]]);

15                     anagram[s] = -1;

16                 }

17                 res.push_back(strs[i]);

18             }

19         }

20         return res;

21     }

22 };