Leetcode--Merge k Sorted Lists (Divide and Conquer/priorityqueue)

Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity.

Branching strategy: Each time you merge a list of two ordered lists until you have only one list left.

public class Solution {public ListNode mergeklists (list<listnode> lists) {//Handling Special cases  if (lists        = = null)             return null;        int length = Lists.size ();        if (length = = 0) return null;        if (length = = 1) return lists.get (0);         listnode Low, high;            while (length! = 1) {//merge the ordered string int index one by one;                for (index = 0, index < LENGTH/2; ++index) {low = Lists.get (2*index);                High = Lists.get (2*index+1);            Lists.set (Index, merge2lists (Low, high));            } if (length%2 = = 1) lists.set (index, Lists.get (length-1));        Length = (length + 1)/2;    } return Lists.get (0);        ListNode merge2lists (ListNode Low, ListNode high) {ListNode result = new ListNode (-1);        ListNode p = result; while (low! = NULL && high ! = null) {if (Low.val < high.val) {p.next = low;                low = Low.next;            p = p.next;                } else {p.next = high;                High = High.next;            p = p.next;        }} if (low = = null) P.next = high;        else P.next = low;    return result.next; }}

Priority queue (or heap sort): http://zh.wikipedia.org/zh/%E5%84%AA%E5%85%88%E4%BD%87%E5%88%97

public class Solution {//This segment of code is from Https://oj.leetcode.com/discuss/25518/13-lines-in-java public   ListNode Mergeklists (list<listnode> lists) {        queue<listnode> heap = new Priorityqueue (New comparator< Listnode> () {            @Override public int compare (ListNode L1, ListNode L2) {                 return l1.val-l2.val;             }        });        ListNode head = new ListNode (0), tail = head;        for (ListNode node:lists) if (node! = null) heap.offer (node);        while (!heap.isempty ()) {            Tail.next = Heap.poll ();            tail = Tail.next;            if (tail.next! = null) Heap.offer (tail.next);        }        return head.next;}    }

Leetcode--Merge k Sorted Lists (Divide and Conquer/priorityqueue)