week 4 solutions

Author: i-mprovising

maximum-depth-of-binary-tree/i-mprovising.py

@@ -0,0 +1,24 @@
+"""
+Time complexity O(n)
+"""
+from collections import deque
+
+class Solution:
+    def maxDepth(self, root: Optional[TreeNode]) -> int:
+        if not root:
+            return 0
+            
+        max_depth = 0
+
+        # bfs
+        q = deque([[root, 1]])
+        while(q):
+            node, depth = q.pop()
+            if max_depth < depth:
+                max_depth = depth
+            if node.left:
+                q.append([node.left, depth+1])
+            if node.right:
+                q.append([node.right, depth+1])
+
+        return max_depth

merge-two-sorted-lists/i-mprovising.py

@@ -0,0 +1,35 @@
+"""
+Time complexity O(n+m)
+"""
+
+class Solution:
+    def mergeTwoLists(self, list1: Optional[ListNode], list2: Optional[ListNode]) -> Optional[ListNode]:
+        if not (list1 or list2):
+            return list1 or list2 # if empty list
+
+        nums = []
+        while(list1 or list2):
+            if not list1:
+                val = list2.val
+                list2 = list2.next
+            elif not list2:
+                val = list1.val
+                list1 = list1.next
+            else:
+                if list1.val <= list2.val:
+                    val = list1.val
+                    list1 = list1.next
+                else:
+                    val = list2.val
+                    list2 = list2.next
+            nums.append(val)
+        
+        head = ListNode(nums[0])
+        node = head
+        if len(nums) == 1:
+            return head
+        for n in nums[1:]:
+            tmp = ListNode(n)
+            node.next = tmp
+            node = tmp
+        return head