[Leetcode 49, medium] Anagrams

Problem:

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

Note: All inputs will be in lower-case.

For example:

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

Output: ["tea","ate","eat"]
Solutions:

1. Two strings are anagrams, if they are same after they are sorted by asending (desending) order. Then, the algrothm is as follows:

Use a map<string, int> to store string which has been sorted and its index. Anytime when a new string is read out from the inputed vector, check whether it is an anagram of an element of the map. If so, push the new string
and the string in the map to the return vector. At the same time, change the recorded index of the string in the map to be -1 inorder not be add once more in the next time.

2. The usage of the STL container map. If you have found a string in the map, you can use the map[string] to read out the other key.



Programs:

vector<string> anagrams(vector<string> &strs) {
        vector<string> rstrs;
        if(strs.size()<=1) return rstrs;
        
        map<string, int> anagrams;
        for(int i=0; i<strs.size(); ++i){
            string curStr=strs[i];
            sort(curStr.begin(), curStr.end());
            if(anagrams.find(curStr)==anagrams.end()){
                //Not found. Add.
                anagrams.insert(std::pair<string, int>(curStr, i));
            }else{
                //Found. Add the original str to rstrs.
                if(anagrams[curStr]>=0){
                    rstrs.push_back(strs[anagrams[curStr]]);
                    anagrams[curStr]=-1;
                }
                rstrs.push_back(strs[i]);
            }
        }
        return rstrs;
    }