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Copy path第五道：(49). Group Anagrams - Medium
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第五道：(49). Group Anagrams - Medium
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Solving method: sorting, hashmap
From NeetCode:
```
class Solution:
def groupAnagrams(self, strs: List[str]) -> List[List[str]]:
ans = defaultdict (list) #mapping charCount to list of anagrams. defauldict it means "Defining a dictionary with values as a list."
for s in strs:
count = [0]*26 #a-z
for c in s:
count [ord(c)-ord("a")]+= 1
ans[tuple(count)].append(s)
return ans.values()
```
From LeetCode:
```python
class Solution:
def groupAnagrams(self, strs: List[str]) -> List[List[str]]:
anagram_map = defaultdict(list)
for word in strs:
sorted_word = ''.join(sorted(word))
anagram_map[sorted_word].append(word)
return list(anagram_map.values())
```
what I’ve learned:
- **defaultdict(list)**
**Using List as default_factory**
When the list class is passed as the default_factory argument, then a defaultdict is created with the values that are list.
`# Defining a dict`
`d =` `defaultdict(list)`
`for` `i in` `range(5):`
`d[i].append(i)`
`print("Dictionary with values as list:")`
`print(d)`
---
**Output:**
```
Dictionary with values as list:
defaultdict(<class 'list'>, {0: [0], 1: [1], 2: [2], 3: [3], 4: [4]})
```
**Using int as default_factory**
When the int class is passed as the default_factory argument, then a defaultdict is created with default value as zero.
`# Defining the dict`
`d =` `defaultdict(int)`
`L =` `[1, 2, 3, 4, 2, 4, 1, 2]`
`# Iterate through the list`
`# for keeping the count`
`for` `i in` `L:`
`# The default value is 0`
`# so there is no need to`
`# enter the key first`
`d[i] +=` `1`
`print(d)`
---
**Output:**
```
defaultdict(<class 'int'>, {1: 2, 2: 3, 3: 1, 4: 2})
```
**Example:**
- link: https://www.geeksforgeeks.org/defaultdict-in-python/
- **append**
-
- **ord**
- Definition and Usage
The `ord()` function returns the number representing the unicode code of a specified character.
---
Syntax
ord(*character*)
Parameter Values
| Parameter | Description |
| --- | --- |
| character | String, any character |
- tuple
- Tuple
Tuples are used to store multiple items in a single variable.
Tuple is one of 4 built-in data types in Python used to store collections of data, the other 3 are [List](https://www.w3schools.com/python/python_lists.asp), [Set](https://www.w3schools.com/python/python_sets.asp), and [Dictionary](https://www.w3schools.com/python/python_dictionaries.asp), all with different qualities and usage.
A tuple is a collection which is ordered and **unchangeable**.
Tuples are written with round brackets.
- join