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leetcode23v2.java
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leetcode23v2.java
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/**
* 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) {
if(lists.length == 0)
return null;
int end = lists.length - 1;
while(end > 0){
int begin = 0;
while(begin < end){
lists[begin] = mergeTwoLists(lists[begin], lists[end]);
begin++;
end--;
}
}
return lists[0];
}
private ListNode mergeTwoLists(ListNode l1, ListNode l2) {
ListNode dummyhead = new ListNode(0);
ListNode p = dummyhead;
while(l1 != null && l2 != null){
if(l1.val < l2.val){
p.next = l1;
l1 = l1.next;
}
else{
p.next = l2;
l2 = l2.next;
}
p = p.next;
}
if(l1 != null)
p.next = l1;
if(l2 != null)
p.next = l2;
return dummyhead.next;
}
}