Add Merge Two Sorted Lists solution

Author: HoonDongKang

merge-two-sorted-lists/HoonDongKang.ts

@@ -0,0 +1,56 @@
+/**
+ * [Problem]: [21] Merge Two Sorted Lists
+ *
+ * (https://leetcode.com/problems/merge-two-sorted-lists/description/)
+ */
+
+class ListNode {
+    val: number;
+    next: ListNode | null;
+    constructor(val?: number, next?: ListNode | null) {
+        this.val = val === undefined ? 0 : val;
+        this.next = next === undefined ? null : next;
+    }
+}
+
+function mergeTwoLists(list1: ListNode | null, list2: ListNode | null): ListNode | null {
+    //시간복잡도 O(m+n)
+    //공간복잡도 O(1)
+    function loopFunc(list1: ListNode | null, list2: ListNode | null): ListNode | null {
+        let current: ListNode = new ListNode();
+        let dummy = current;
+
+        while (list1 !== null && list2 !== null) {
+            if (list1.val < list2.val) {
+                current.next = list1;
+                list1 = list1.next;
+            } else {
+                current.next = list2;
+                list2 = list2.next;
+            }
+
+            current = current.next;
+        }
+
+        current.next = list1 !== null ? list1 : list2;
+
+        return dummy.next;
+    }
+
+    //시간복잡도 O(m+n)
+    //공간복잡도 O(m+n)
+    function recursionFunc(list1: ListNode | null, list2: ListNode | null): ListNode | null {
+        if (list1 === null) return list2;
+        if (list2 === null) return list1;
+
+        if (list1.val < list2.val) {
+            list1.next = recursionFunc(list1.next, list2);
+            return list1;
+        } else {
+            list2.next = recursionFunc(list1, list2.next);
+            return list2;
+        }
+    }
+
+    return recursionFunc(list1, list2);
+}