[sangbeenmoon] WEEK 1 Solutions

contains-duplicate/sangbeenmoon.py

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+# time : O(n)
+# space : O(n)
+class Solution:
+    def containsDuplicate(self, nums: List[int]) -> bool:
+        d = {}
+        for num in nums:
+            if num in d:
+                return True
+            else:
+                d[num] = True
+        return False

top-k-frequent-elements/sangbeenmoon.py

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+# idea
+# 1. 빈도수를 dict 에 저장한다.
+# 2. 빈도수 내림차순으로 정렬한다.
+# 3. 2에서 정렬한 entry 중 1번째, 2번째, ... k 번째 key 값을 모아서 List 로 반환한다.
+# time : O(nlogn)
+# space : O(n)
+class Solution:
+    def topKFrequent(self, nums: List[int], k: int) -> List[int]:
+        count_dict = {}
+
+        for num in nums:
+            if num in count_dict:
+                count_dict[num] = count_dict[num] + 1
+            else:
+                count_dict[num] = 1
+
+        tuple_list = []
+
+        for (count_key, count_value) in count_dict.items():
+            tuple_list.append((count_key, count_value))
+
+        sorted_tuple_list = sorted(tuple_list, key=lambda x: x[1], reverse=True)
+        answer = []
+
+        for i in range(k):
+            answer.append(sorted_tuple_list[i][0])
+
+        return answer
+
+
+