Merge pull request #1225 from krokerdile/main

[krokerdile] WEEK 02 solutions

Author: krokerdile

3sum/krokerdile.py

@@ -0,0 +1,58 @@
+class Solution:
+    def threeSum(self, nums: List[int]) -> List[List[int]]:
+        nums.sort()
+        res = []
+        n = len(nums)
+
+        for i in range(n):
+            if i > 0 and nums[i] == nums[i-1]:
+                continue
+
+            target = -nums[i]
+            seen = set()
+            j = i + 1
+
+            while j < n:
+                complement = target - nums[j]
+                if complement in seen:
+                    res.append([nums[i], complement, nums[j]])
+                    while j + 1 < n and nums[j] == nums[j+1]:
+                        j += 1
+                seen.add(nums[j])
+                j += 1
+        return list(set(tuple(x) for x in res))
+    
+
+class Solution:
+    def threeSum(self, nums: List[int]) -> List[List[int]]:
+        nums.sort()
+        result = []
+
+        for i in range(len(nums)):
+            # 중복된 첫 번째 수는 skip
+            if i > 0 and nums[i] == nums[i - 1]:
+                continue
+
+            left, right = i + 1, len(nums) - 1
+
+            while left < right:
+                total = nums[i] + nums[left] + nums[right]
+
+                if total == 0:
+                    result.append([nums[i], nums[left], nums[right]])
+
+                    # 중복된 두 번째, 세 번째 수 건너뛰기
+                    while left < right and nums[left] == nums[left + 1]:
+                        left += 1
+                    while left < right and nums[right] == nums[right - 1]:
+                        right -= 1
+
+                    left += 1
+                    right -= 1
+
+                elif total < 0:
+                    left += 1  # 합이 작으면 왼쪽을 오른쪽으로
+                else:
+                    right -= 1  # 합이 크면 오른쪽을 왼쪽으로
+
+        return result

climbing-stairs/krokerdile.py

@@ -0,0 +1,10 @@
+class Solution:
+    def climbStairs(self, n: int) -> int:
+        one, two = 1,1
+
+        for i in range(n-1):
+            temp = one;
+            one = one + two;
+            two = temp;
+
+        return one;

product-of-array-except-self/krokerdile.py

@@ -0,0 +1,18 @@
+class Solution:
+    def productExceptSelf(self, nums: List[int]) -> List[int]:
+        n = len(nums)
+        answer = [1] * n
+        
+        # 1. 왼쪽 곱 저장
+        left_product = 1
+        for i in range(n):
+            answer[i] = left_product
+            left_product *= nums[i]
+
+        # 2. 오른쪽 곱을 곱해주기
+        right_product = 1
+        for i in reversed(range(n)):
+            answer[i] *= right_product
+            right_product *= nums[i]
+        
+        return answer

valid-anagram/krokerdile.py

@@ -0,0 +1,13 @@
+class Solution:
+    def isAnagram(self, s: str, t: str) -> bool:
+        a = {}
+        b = {}
+
+        if len(s) != len(t):
+            return False
+
+        for i in range(len(s)):
+            a[s[i]] = a.get(s[i], 0) + 1
+            b[t[i]] = b.get(t[i], 0) + 1
+
+        return a == b

validate-binary-search-tree/krokerdile.py

@@ -0,0 +1,15 @@
+class Solution:
+    def isValidBST(self, root: Optional[TreeNode]) -> bool:
+        def validate(node, low, high):
+            if not node:
+                return True
+            
+            # 현재 노드의 값이 범위를 벗어나면 False
+            if not (low < node.val < high):
+                return False
+
+            # 왼쪽 서브트리는 최대값을 현재 노드 값으로 제한
+            # 오른쪽 서브트리는 최소값을 현재 노드 값으로 제한
+            return validate(node.left, low, node.val) and validate(node.right, node.val, high)
+
+        return validate(root, float('-inf'), float('inf'))