> For the complete documentation index, see [llms.txt](https://maksimdan.gitbook.io/interview-practice-problems/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://maksimdan.gitbook.io/interview-practice-problems/coding_practice_questions/interview_questions_4/group-anagrams.md).

# Group Anagrams

**10.2 Group Anagrams:** Write a method to sort an array of strings so that all the anagrams are next to each other.

* O(NlogN) time?, O(N) extra space
* One way of doing this is first sort the strings, and pair them into a map.
* Then we can sort the map by its second value, then return its first value.

```cpp
typedef std::pair<std::string, string> p;
struct Comp {
    bool operator()(const p &left, const p &right) const {
        return left.first < right.second;
    }
};

void group_anagrams(vector<string> &strings) {
    map<string, string> word_anagram;

    for (int i = 0; i < strings.size(); i++) {
        string cpy = strings.at(i);
        sort(strings.at(i).begin(), strings.at(i).end());
        word_anagram.insert( { { cpy }, { strings.at(i) } });
    }

    // dump into vector in order to make it sortable
    vector<pair<string, string>> cpy(word_anagram.begin(), word_anagram.end());

    sort(cpy.begin(), cpy.end(), Comp());

    int count = 0;
    for (auto &i : cpy) {
        strings.at(count++) = i.first;
    }

}


int main() {
    vector<string> words = {"could", "cloud", "dance", "caned", "own", "now", "clams", "calms", "wings", "swing", "a" };

    group_anagrams(words);
    print(words);
}
```


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://maksimdan.gitbook.io/interview-practice-problems/coding_practice_questions/interview_questions_4/group-anagrams.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.