You are given an array of k linked-lists lists, each linked-list is sorted in ascending order.
Merge all the linked-lists into one sorted linked-list and return it.
Example 1:
Input: lists = [[1,4,5],[1,3,4],[2,6]] Output: [1,1,2,3,4,4,5,6] Explanation: The linked-lists are: [ 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.length0 <= k <= 1040 <= lists[i].length <= 500-104 <= lists[i][j] <= 104lists[i] is sorted in ascending order.lists[i].length will not exceed 104.
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 temphead = lists[i];
while(temphead!=null){
pq.add(temphead);
temphead=temphead.next;
}
}
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;
}
}
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