[kimjunyoung90] WEEK 04 solutions

maximum-depth-of-binary-tree/kimjunyoung90.java

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+public class Solution {
+    public int maxDepth(TreeNode root) {
+        if (root == null) return 0;
+        return 1 + Math.max(maxDepth(root.left), maxDepth(root.right));
+    }
+}
+
+class TreeNode {
+    int val;
+    TreeNode left;
+    TreeNode right;
+
+    TreeNode() {
+    }
+
+    TreeNode(int val) {
+        this.val = val;
+    }
+
+    TreeNode(int val, TreeNode left, TreeNode right) {
+        this.val = val;
+        this.left = left;
+        this.right = right;
+    }
+}

merge-two-sorted-lists/kimjunyoung90.java

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+public class Solution {
+    public ListNode mergeTwoLists(ListNode list1, ListNode list2) {
+        //1. null 체크
+        if(list1 == null || list2 == null) {
+            return list1 != null ? list1 : list2;
+        }
+        //1. 값 비교
+        if(list1.val < list2.val) {
+            //다음 Node 비교
+            list1.next = mergeTwoLists(list1.next, list2);
+            return list1;
+        } else {
+            list2.next = mergeTwoLists(list1, list2.next);
+            return list2;
+        }
+    }
+}
+
+class ListNode {
+    int val;
+    ListNode next;
+    ListNode() {}
+    ListNode(int val) { this.val = val; }
+    ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+}