# 49. Group Anagrams

{% hint style="info" %}
针对这种在顺序上做文章的，首先要进行排序，再做操作

Key idea: `hashmap()`
{% endhint %}

### Solution:

1. traverse all elements of strs
2. sort each word by letters
3. add to hashmap, the words composed with same letters will be mapped to same key-item
4. covert to `result` list

```python
class Solution:
    def groupAnagrams(self, strs: List[str]) -> List[List[str]]:
        d = {}
        for x in strs:
            tmp = sorted(x)
            tmp = "".join(tmp)
            if tmp not in d:
                d[tmp] = [x]
            else:
                d[tmp].append(x)
        
        result = []
        for key in d.keys():
            result.append(d[key])
            
        return result
```

Time complexity = $$O(n)$$ , if `sorted()` is $$O(1)$$ , Space complesity = $$O(n)$$ 

{% hint style="danger" %}
`list.sort()` change the list, `sorted(list)` doesn't change the list.

`list.reverse()` change the list, `reversed(list)` doesn't change the list.

`sorted(string)` converts string to a list.

`separator.join(list)` means convert list to a string combining by separator. For example, `"".join(['a', 'b', 'c']) = "abc".`
{% endhint %}


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