[sm9171] Week 4 solutions

maximum-depth-of-binary-tree/sm9171.java

@@ -0,0 +1,10 @@
+class Solution {
+    public int maxDepth(TreeNode root) {
+        if (root == null) {
+            return 0;
+        }
+        int leftDepth = maxDepth(root.left);
+        int rightDepth = maxDepth(root.right);
+        return Math.max(leftDepth, rightDepth) + 1;
+    }
+}

merge-two-sorted-lists/sm9171.java

@@ -0,0 +1,20 @@
+class Solution {
+    public ListNode mergeTwoLists(ListNode list1, ListNode list2) {
+        ListNode dummy = new ListNode(-1);
+        ListNode node = dummy;
+
+        while (list1 != null && list2 != null) {
+            if (list1.val < list2.val) {
+                node.next = list1;
+                list1 = list1.next;
+            } else {
+                node.next = list2;
+                list2 = list2.next;
+            }
+            node = node.next;
+        }
+
+        node.next = list1 != null ? list1 : list2;
+        return dummy.next;
+    }
+}