refactor 23

Author: fishercoder1534

README.md

@@ -579,7 +579,7 @@ Your ideas/fixes/algorithms are more than welcome!
 |26|[Remove Duplicates from Sorted Array](https://leetcode.com/problems/remove-duplicates-from-sorted-array/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_26.java)|O(n)|O(1)|Easy| Array 
 |25|[Reverse Nodes in k-Group](https://leetcode.com/problems/reverse-nodes-in-k-group/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_25.java)|O(n)|O(1)| Hard | Recursion, LinkedList
 |24|[Swap Nodes in Pairs](https://leetcode.com/problems/swap-nodes-in-pairs/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_24.java)|O(n)|O(h)|Medium| Recursion, LinkedList
-|23|[Merge k Sorted Lists](https://leetcode.com/problems/merge-k-sorted-lists/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_23.java)|O(n*logk)|O(logk)|Hard|Heap
+|23|[Merge k Sorted Lists](https://leetcode.com/problems/merge-k-sorted-lists/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_23.java)|O(n*logk)|O(k)|Hard|Heap
 |22|[Generate Parentheses](https://leetcode.com/problems/generate-parentheses/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_22.java)|TBD|O(n)|Medium|Backtracking
 |21|[Merge Two Sorted Lists](https://leetcode.com/problems/merge-two-sorted-lists/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_21.java)|O(n)|O(h)|Easy| Recursion
 |20|[Valid Parentheses](https://leetcode.com/problems/valid-parentheses/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_20.java)|O(n)|O(n)|Easy|Stack

src/main/java/com/fishercoder/solutions/_23.java

@@ -5,29 +5,37 @@
 import java.util.Comparator;
 import java.util.PriorityQueue;
 
-/**Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity.*/
+/**
+ * 23. Merge k Sorted Lists
+ *
+ * Merge k sorted linked lists and return it as one sorted list.
+ * Analyze and describe its complexity.*/
 
 public class _23 {
+
     public ListNode mergeKLists(ListNode[] lists) {
-        PriorityQueue<ListNode> heap = new PriorityQueue(new Comparator<ListNode>(){
+        PriorityQueue<ListNode> heap = new PriorityQueue(new Comparator<ListNode>() {
             @Override
             public int compare(ListNode o1, ListNode o2) {
                 return o1.val - o2.val;
             }
         });
-        
-        for(ListNode node : lists){
-            if(node != null) heap.offer(node);
+
+        for (ListNode node : lists) {
+            if (node != null) heap.offer(node);
         }
-        
+
         ListNode pre = new ListNode(-1);
         ListNode temp = pre;
-        while(!heap.isEmpty()){
+        while (!heap.isEmpty()) {
             ListNode curr = heap.poll();
-            temp.next = curr;
+            temp.next = new ListNode(curr.val);
+            if (curr.next != null) {
+                heap.offer(curr.next);
+            }
             temp = temp.next;
-            if(curr.next != null) heap.offer(curr.next);
         }
         return pre.next;
     }
+
 }