[HodaeSsi] Week 10

invert-binary-tree/HodaeSsi.py

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+from typing import Optional
+
+class TreeNode:
+    def __init__(self, val=0, left=None, right=None):
+        self.val = val
+        self.left = left
+        self.right = right
+
+# 시간 복잡도 : O(n)
+# 공간 복잡도 : O(n)
+class Solution:
+	# 오른쪽부터 탐색하는 전위 순회 구현
+	def invertPreOrder(self, src: TreeNode, des: TreeNode) -> None:
+		des.val = src.val
+		if src.right:
+			des.left = TreeNode()
+			self.invertPreOrder(src.right, des.left)
+		if src.left:
+			des.right = TreeNode()
+			self.invertPreOrder(src.left, des.right)
+
+	def invertTree(self, root: Optional[TreeNode]) -> Optional[TreeNode]:
+		if not root:
+			return None
+		des = TreeNode()
+		self.invertPreOrder(root, des)
+		return des
+

search-in-rotated-sorted-array/HodaeSsi.py

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+from typing import List
+
+# 시간 복잡도 : O(log n) (* 최대 세번의 이진 탐색 수행)
+# 공간 복잡도 : O(1)
+class Solution:
+	def find_pivot_idx(self, src_list: List[int], start_idx: int, end_idx: int) -> int:
+		if start_idx == end_idx:
+			return start_idx
+		mid_idx = (start_idx + end_idx) // 2
+		if src_list[mid_idx] > src_list[end_idx]:
+			return self.find_pivot_idx(src_list, mid_idx + 1, end_idx)
+		else:
+			return self.find_pivot_idx(src_list, start_idx, mid_idx)
+
+
+	def find_target_idx(self, src_list: List[int], start_idx: int, end_idx: int, target) -> int:
+		if start_idx > end_idx:
+			return -1
+		if start_idx == end_idx:
+			if src_list[start_idx] == target:
+				return start_idx
+			else:
+				return -1
+
+		mid_idx = (start_idx + end_idx) // 2
+		if src_list[mid_idx] == target:
+			return mid_idx
+		elif src_list[mid_idx] > target:
+			return self.find_target_idx(src_list, start_idx, mid_idx - 1, target)
+		else:
+			return self.find_target_idx(src_list, mid_idx + 1, end_idx, target)
+
+
+	def search(self, nums: List[int], target: int) -> int:
+		if nums[0] > nums[len(nums) - 1]:
+			pivot_idx = self.find_pivot_idx(nums, 0, len(nums) - 1)
+			left = self.find_target_idx(nums, 0, pivot_idx - 1, target)
+			if left != -1:
+				return left
+			else:
+				return self.find_target_idx(nums, pivot_idx, len(nums) - 1, target)
+		else:
+			return self.find_target_idx(nums, 0, len(nums) - 1, target)
+