[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"]

class Solution {
public:
    vector<string> anagrams(vector<string> &strs) {
        string s;
        map<string, int> anagram;
        vector<string> res;
        for (int i = 0; i < strs.size(); ++i) {
            s = strs[i];
            sort(s.begin(), s.end());
            if (anagram.find(s) == anagram.end()) {
                anagram[s] = i;
            } else {
                if (anagram[s] >= 0) {
                    res.push_back(strs[anagram[s]]);
                    anagram[s] = -1;
                }
                res.push_back(strs[i]);
            }
        }
        return res;
    }
};