[Leetcode] Anagrams

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

Note: All inputs will be in lower-case.

這題先得知道啥叫Anagrams，知道后其實很簡單。

首先簡單介紹一下Anagram（回文構詞法）。Anagrams是指由顛倒字母順序組成的單詞，比如“dormitory”顛倒字母順序會變成“dirty room”，“tea”會變成“eat”。

回文構詞法有一個特點：單詞里的字母的種類和數目沒有改變，只是改變了字母的排列順序。

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;
    }
};