Create 23-Merge-k-Sorted-Lists.cs

csharp/23-Merge-k-Sorted-Lists.cs

@@ -0,0 +1,65 @@
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ * public int val;
+ * public ListNode next;
+ * public ListNode(int val=0, ListNode next=null) {
+ * this.val = val;
+ * this.next = next;
+ * }
+ * }
+ */
+
+public class Solution {
+ public ListNode MergeKLists(ListNode[] lists) {
+ if (lists.Length == 0)
+ {
+ return null;
+ }
+
+ while (lists.Length > 1)
+ {
+ var mergedLists = new ListNode[(lists.Length + 1) / 2];
+ for (int i = 0; i < lists.Length; i += 2)
+ {
+ var l1 = lists[i];
+ var l2 = (i + 1 < lists.Length) ? lists[i + 1] : null;
+ mergedLists[i/2] = (MergeLists(l1, l2));
+ }
+ lists = mergedLists;
+ }
+
+ return lists[0];
+ }
+
+ public ListNode MergeLists(ListNode l1, ListNode l2)
+ {
+ var sorted = new ListNode();
+ var current = sorted;
+
+ while (l1 != null && l2 != null)
+ {
+ if (l1.val <= l2.val)
+ {
+ current.next = l1;
+ l1 = l1.next;
+ }
+ else
+ {
+ current.next = l2;
+ l2 = l2.next;
+ }
+ current = current.next;
+ }
+
+ if (l1 != null)
+ {
+ current.next = l1;
+ } else 
+ {
+ current.next = l2;
+ }
+
+ return sorted.next;
+ }
+}