Merge pull request #1187 from sejineer/main

[sejineer] Week 01 solutions

Author: sejineer

contains-duplicate/sejineer.py

@@ -0,0 +1,18 @@
+"""
+시간 복잡도 O(n)
+공간 복잡도 O(n)
+
+코드 가독성 향상 코드
+class Solution:
+    def containsDuplicate(self, nums: List[int]) -> bool:
+        return len(nums) != len(set(nums))
+"""
+class Solution:
+    def containsDuplicate(self, nums: List[int]) -> bool:
+        check = set([])
+        for i in nums:
+            if i not in check:
+                check.add(i)
+            else:
+                return True
+        return False

house-robber/sejineer.py

@@ -0,0 +1,24 @@
+"""
+시간 복잡도 O(N)
+공간 복잡도 O(N)
+
+
+"""
+
+class Solution:
+    def rob(self, nums: List[int]) -> int:
+        memo = {}
+
+        def backtracking(k: int) -> int:
+            if k >= len(nums):
+                return 0
+            if k in memo:
+                return memo[k]
+            
+            rob = nums[k] + backtracking(k + 2)
+            skip = backtracking(k + 1)
+
+            memo[k] = max(rob, skip)
+            return memo[k]
+        
+        return backtracking(0)

longest-consecutive-sequence/sejineer.py

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+"""
+시간 복잡도 O(N)
+공간 복잡도 O(N)
+"""
+class Solution:
+    def longestConsecutive(self, nums: List[int]) -> int:
+        nums_set = set(nums)
+        result = 0
+
+        for i in nums_set:
+            if i - 1 not in nums_set:
+                length = 1
+                while i + length in nums_set:
+                    length += 1
+                result = max(result, length)
+        
+        return result

top-k-frequent-elements/sejineer.py

@@ -0,0 +1,44 @@
+"""
+시간 복잡도 O(N)
+공간 복잡도 O(N)
+
+Priority Queue 를 이용한 풀이
+시간 복잡도 O(Nlog(N))
+공간 복잡도 O(N)
+from queue import PriorityQueue
+from collections import Counter
+
+class Solution:
+    def topKFrequent(self, nums: List[int], k: int) -> List[int]:
+        counter = Counter(nums)
+        que = PriorityQueue()
+
+        for num, freq in counter.items():
+            que.put((-freq, num))
+        
+        res = []
+
+        for _ in range(k):
+            res.append(que.get()[1])
+
+        return res
+"""
+from collections import Counter
+
+class Solution:
+    def topKFrequent(self, nums: List[int], k: int) -> List[int]:
+        freq_map = Counter(nums)
+
+        bucket = [[] for _ in range(len(nums) + 1)]
+
+        for num, freq in freq_map.items():
+            bucket[freq].append(num)
+
+        result = []
+
+        for i in range(len(bucket) - 1, -1, -1):
+            if bucket[i]:
+                for num in bucket[i]:
+                    result.append(num)
+                    if len(result) == k:
+                        return result

two-sum/sejineer.py

@@ -0,0 +1,14 @@
+"""
+시간 복잡도 O(n)
+공간 복잡도 O(n)
+"""
+class Solution:
+    def twoSum(self, nums: List[int], target: int) -> List[int]:
+        nums_map = {}
+
+        for i, v in enumerate(nums):
+            x = target - v
+            if x in nums_map:
+                j = nums_map[x]
+                return [j, i]
+            nums_map[v] = i