Feat: 23. Merge k Sorted Lists

Author: HC-kang

merge-k-sorted-lists/HC-kang.ts

@@ -0,0 +1,39 @@
+// 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;
+//   }
+// }
+
+/**
+ * https://leetcode.com/problems/merge-k-sorted-lists
+ * T.C. O(n * k^2) n: average length of list, k: number of lists
+ * S.C. O(k)
+ */
+function mergeKLists(lists: Array<ListNode | null>): ListNode | null {
+  if (lists.length === 0) return null;
+  if (lists.length === 1) return lists[0];
+  return lists.reduce((acc, cur) => mergeTwoLists(acc, cur), null);
+
+  function mergeTwoLists(list1: ListNode | null, list2: ListNode | null): ListNode | null {
+    const head = new ListNode();
+    let current = head;
+
+    while (list1 && list2) {
+      if (list1.val < list2.val) {
+        current.next = list1;
+        list1 = list1.next;
+      } else {
+        current.next = list2;
+        list2 = list2.next;
+      }
+      current = current.next;
+    }
+
+    current.next = list1 || list2;
+
+    return head.next;
+  }
+}