feat: week4 easy 문제 풀이

Author: jinah92

merge-two-sorted-lists/jinah92.py

@@ -0,0 +1,18 @@
+# O(m+n) times, O(1) spaces
+class Solution:
+    def mergeTwoLists(self, list1: Optional[ListNode], list2: Optional[ListNode]) -> Optional[ListNode]:
+        dummy = ListNode(None)
+        node = dummy
+
+        while list1 and list2:
+            if list1.val < list2.val:
+                node.next = list1
+                list1 = list1.next
+            else:
+                node.next = list2
+                list2 = list2.next
+
+            node = node.next
+        
+        node.next = list1 or list2
+        return dummy.next

missing-number/jinah92.py

@@ -0,0 +1,12 @@
+# O(n) times, O(n) spaces
+class Solution:
+    def missingNumber(self, nums: List[int]) -> int:
+        nums_keys = dict.fromkeys(nums,0)
+        last = 0
+        
+        for i in range(len(nums)):
+            if not i in nums_keys:
+                return i
+            last += 1
+        
+        return last