3주차 solution

Author: Donghae0230

combination-sum/Donghae0230.py

@@ -0,0 +1,16 @@
+class Solution:
+    def combinationSum(self, candidates: List[int], target: int) -> List[List[int]]:
+        def backtrack(start, combination):
+            if sum(combination) > target:
+                return
+            if sum(combination) == target:
+                result.append(combination[:]) 
+                return 
+            for i in range(start, len(candidates)):
+                combination.append(candidates[i])
+                backtrack(i, combination)
+                combination.pop()
+            
+        result = []
+        backtrack(0, [])
+        return result

number-of-1-bits/Donghae0230.py

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+# 시간 복잡도 O(n): 2로 반복해서 나눠야함
+# 공간 복잡도 O(n): result 생성
+
+class Solution:
+    def devide_by_2 (self, n, temp):
+        global val
+        if n > 1 :
+            val = n // 2
+            remain = n % 2
+            temp.append(remain)
+            return self.devide_by_2(val, temp)
+        temp.append(val)
+        return val, temp
+
+    def hammingWeight(self, n: int) -> int:
+        result = []
+        n, result = self.devide_by_2(n, result)
+        return result.count(1)
+        

valid-palindrome/Donghae0230.py

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+# 시간복잡도 O(n): reversed 함수 사용
+# 공간복잡도 O(n): cleaned_s, reversed_s 사용
+import re
+
+class Solution:
+    def isPalindrome(self, s: str) -> bool:
+        cleaned_s = re.sub(r'[^a-zA-Z0-9]', '', s.lower())
+        reversed_s = ''.join(reversed(cleaned_s))
+        if cleaned_s == reversed_s:
+            return True
+        else:
+            return False