leetcode Merge k Sorted Lists

题目链接

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
public class Solution {
       public ListNode mergeKLists(ListNode[] lists) {
        int n=lists.length;
        ListNode result=new ListNode(Integer.MAX_VALUE);
        ListNode pointer=result;
        int nullListCount=0;
        boolean isNull[]=new boolean[n];


        Comparator<record> OrderIsdn=new Comparator<record>() {
            public int compare(record o1, record o2) {  
                // TODO Auto-generated method stub  
                int numbera = o1.value;  
                int numberb = o2.value;  
                if(numberb < numbera)  
                {  
                    return 1;  
                }  
                else if(numberb>numbera)  
                {  
                    return -1;  
                }  
                else  
                {  
                    return 0;  
                }  

            }  
        };

        PriorityQueue<record> priorityQueue=new PriorityQueue<Solution.record>(OrderIsdn);



        for(int i=0;i<n;i++)
        {
            if(lists[i]==null)
            {
                isNull[i]=true;
                nullListCount++;
            }
            else
            {
                priorityQueue.add(new record(lists[i].val,i));
            }
        }





        while(nullListCount!=n)
        {
            record aRecord=priorityQueue.poll();

            int Min=aRecord.value;
            int MinIndex=aRecord.index;
            pointer.next=new ListNode(Min);
            pointer=pointer.next;
            lists[MinIndex]=lists[MinIndex].next;
            if(lists[MinIndex]==null)
            {
                isNull[MinIndex]=true;
                nullListCount++;
            }
            else
            {
                priorityQueue.add(new record(lists[MinIndex].val, MinIndex));
            }
        }
        return result.next;
    }


    class record
    {
        int index;
        int value;
        record(int value,int index)
        {
            this.index=index;
            this.value=value;
        }
    }
}