[thispath98] Week 1

contains-duplicate/thispath98.py

@@ -0,0 +1,15 @@
+"""
+# Time Complexity: O(N)
+- N번 순회
+# Space Compelexity: O(N)
+- 최악의 경우 (중복된 값이 없을 경우) N개 저장
+"""
+class Solution:
+    def containsDuplicate(self, nums: List[int]) -> bool:
+        num_dict = {}
+        for num in nums:
+            if num not in num_dict:
+                num_dict[num] = True
+            else:
+                return True
+        return False

house-robber/thispath98.py

@@ -0,0 +1,19 @@
+"""
+# Time Complexity: O(N)
+- N개의 개수를 가지는 dp 리스트를 만들고, 이를 순회
+# Space Compelexity: O(N)
+- N개의 dp 리스트 저장
+"""
+class Solution:
+    def rob(self, nums: List[int]) -> int:
+        if len(nums) == 1:
+            return nums[0]
+
+        dp = [0 for _ in range(len(nums))]
+        dp[0] = nums[0]
+        dp[1] = max(nums[0], nums[1])
+
+        for i in range(len(nums) - 2):
+            dp[i + 2] = max(dp[i] + nums[i + 2], dp[i + 1])
+
+        return max(dp[-2], dp[-1])

longest-common-subsequence/thispath98.py

@@ -0,0 +1,37 @@
+"""
+# Time Complexity: O(N)
+- lce_dict 생성: N
+- N개의 key에 대하여 순회하면서 값 확인: N
+# Space Compelexity: O(k)
+- 중복되지 않은 key k개 저장
+"""
+class Solution:
+    def longestConsecutive(self, nums: List[int]) -> int:
+        if not nums:
+            return 0
+
+        lce_dict = {}
+        for num in nums:
+            lce_dict[num] = True
+
+        answer = 0
+        for num in nums:
+            cur_lce = 1
+            if lce_dict.pop(num, None) is None:
+                continue
+
+            down_num = num - 1
+            while down_num in lce_dict:
+                cur_lce += 1
+                lce_dict.pop(down_num)
+                down_num -= 1
+
+            up_num = num + 1
+            while up_num in lce_dict:
+                cur_lce += 1
+                lce_dict.pop(up_num)
+                up_num += 1
+
+            answer = answer if answer > cur_lce else cur_lce
+
+        return answer

top-k-frequent-elements/thispath98.py

@@ -0,0 +1,16 @@
+"""
+# Time Complexity: O(N log N)
+- Counter 생성: N번 순회
+- most common 연산: N log N
+# Space Compelexity: O(N)
+- 최악의 경우 (중복된 값이 없을 경우) N개 저장
+"""
+from collections import Counter
+
+
+class Solution:
+    def topKFrequent(self, nums: List[int], k: int) -> List[int]:
+        count_dict = Counter(nums)
+        top_k_list = count_dict.most_common(k)
+        answer = [key for key, value in top_k_list]
+        return answer

valid-palindrome/thispath98.py

@@ -0,0 +1,13 @@
+"""
+# Time Complexity: O(N)
+- N개의 char를 각각 한번씩 순회
+# Space Compelexity: O(N)
+- 최악의 경우 (공백이 없을 경우) N개의 char 저장
+"""
+class Solution:
+    def isPalindrome(self, s: str) -> bool:
+        string = [char.lower() for char in s if char.isalnum()]
+        for i in range(len(string) // 2):
+            if string[i] != string[-i - 1]:
+                return False
+        return True