### LeetCode Challenge #23. Merge k Sorted Lists

You are given an array of `k` linked-lists `lists`, each linked-list is sorted in ascending order.

Example 1:

```Input: lists = [[1,4,5],[1,3,4],[2,6]]
Output: [1,1,2,3,4,4,5,6]
[
1->4->5,
1->3->4,
2->6
]
merging them into one sorted list:
1->1->2->3->4->4->5->6
```

Example 2:

```Input: lists = []
Output: []
```

Example 3:

```Input: lists = [[]]
Output: []
```

Constraints:

• `k == lists.length`
• `0 <= k <= 104`
• `0 <= lists[i].length <= 500`
• `-104 <= lists[i][j] <= 104`
• `lists[i]` is sorted in ascending order.
• The sum of `lists[i].length` will not exceed `104`.
##### Video Solution
###### Java Solution
```				```
class Solution {
public ListNode mergeKLists(ListNode[] lists) {
if(lists.length == 0 ){
return null;
}else if ( lists.length == 1){
return lists[0];
}

PriorityQueue<ListNode> pq = new PriorityQueue<>((a,b)->a.val-b.val);

for(int i=0;i<lists.length;i++){
}
}
ListNode dummy = new ListNode(-1);
ListNode ans = dummy ;

while(pq.size()>0){
ListNode node = pq.remove();
dummy.next = node ;
dummy = dummy.next;
}
dummy.next = null;
return ans.next;
}
}
```
```