49 字母异位词分组

https://leetcode.cn/leetbook/read/top-interview-questions-medium/xvaszc/

cost: 14m10s

class Solution {
public:
    vector<vector<string>> groupAnagrams(vector<string>& strs) {
        unordered_map<string, vector<int>> m;
        for (int i = 0; i < strs.size(); i++) {
            string str = strs[i];
            std::sort(str.begin(), str.end());
            if (!m.count(str)) {
                m[str] = {};
            }
            m[str].push_back(i);
        }
        vector<vector<string>> r;
        for (const auto [_, indexes] : m) {
            vector<string> vec;
            for (const int i : indexes) {
                vec.push_back(strs[i]);
            }
            r.push_back(vec);
        }
        return r;
    }
};