feat: 2주차 풀이 완료

Author: gusdn0828

invert-binary-tree/saysimple.py

@@ -0,0 +1,20 @@
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+# TC, SC: O(n), O(n)
+class Solution:
+    def invertTree(self, root: Optional[TreeNode]) -> Optional[TreeNode]:
+        if not root:
+            return None
+
+        left = root.left
+        root.left = root.right
+        root.right = left
+
+        self.invertTree(root.left)
+        self.invertTree(root.right)
+
+        return root

linked-list-cycle/saysimple.py

@@ -0,0 +1,20 @@
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.next = None
+# TC, SC: O(n), O(1)
+class Solution:
+    def hasCycle(self, head: Optional[ListNode]) -> bool:
+        if not head:
+            return None
+
+        head.pos = 0
+
+        while head.next:
+            if hasattr(head.next, "pos"):
+                return True
+            head.next.pos = head.pos + 1
+            head = head.next
+
+        return False

merge-two-sorted-lists/saysimple.py

@@ -3,6 +3,7 @@
 #     def __init__(self, val=0, next=None):
 #         self.val = val
 #         self.next = next
+# TC, SC: O(n), O(n)
 class Solution:
     def mergeTwoLists(self, list1: Optional[ListNode], list2: Optional[ListNode]) -> Optional[ListNode]:
         if not (list1 and list2):

valid-parentheses/saysimple.py

@@ -1,3 +1,4 @@
+# TC, SC: O(n), O(n)
 class Solution:
     def isValid(self, s: str) -> bool:
         arr = []