49. Group Anagrams

49_group_anagrams/problem.md

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+## 問題: [49. Group Anagrams](https://leetcode.com/problems/group-anagrams/description/)

49_group_anagrams/step1.md

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+# Step 1
+
+- string毎に、アルファベットが何回出たかをa-zの配列に記録する
+- dictに配列をキーとする、stringを追加していく
+
+```python
+class Solution:
+    def groupAnagrams(self, strs: List[str]) -> List[List[str]]:
+        unordered_characters_to_words = defaultdict(list)
+        for word in strs:
+            key = [0] * 26
+            for character in word:
+                key[ord(character) - ord("a")] += 1
+            unordered_characters_to_words[tuple(key)].append(word)
+        return list(unordered_characters_to_words.values())
+```
+
+時間計算量: $O(mn)$
+
+空間計算量: $O(mn)$
+
+アルゴリズム最大実行時間(概算): 時間計算量 / Pythonの1秒あたりの計算ステップ数 -> $(10^4 \times 100) \div 10,000,000 = 0.1 (s)$

49_group_anagrams/step2.md

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+# Step 2
+
+```python
+class Solution:
+    def groupAnagrams(self, strs: List[str]) -> List[List[str]]:
+        signature_to_words = defaultdict(list)
+        for word in strs:
+            key = [0] * 26
+            for character in word:
+                key[ord(character) - ord("a")] += 1
+            signature_to_words[tuple(key)].append(word)
+        return list(signature_to_words.values())
+
+```
+
+時間計算量: $O(mn)$
+
+空間計算量: $O(mn)$
+
+アルゴリズム最大実行時間(概算): 時間計算量 / Pythonの1秒あたりの計算ステップ数 -> $(10^4 \times 100) \div 10,000,000 = 0.1 (s)$

49_group_anagrams/step3.md

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+# Step 3
+
+```python
+class Solution:
+    def groupAnagrams(self, strs: List[str]) -> List[List[str]]:
+        signature_to_words = defaultdict(list)
+        for word in strs:
+            key = [0] * 26
+            for character in word:
+                key[ord(character) - ord("a")] += 1
+            signature_to_words[tuple(key)].append(word)
+        return list(signature_to_words.values())
+
+```
+
+1回目: 1分　47秒
+
+2回目: 1分　28秒
+
+3回目: 1分　29秒