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21.merge-two-sorted-lists.java
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21.merge-two-sorted-lists.java
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/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode() {}
* ListNode(int val) { this.val = val; }
* ListNode(int val, ListNode next) { this.val = val; this.next = next; }
* }
*/
class Solution {
public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
if(l1 == null)
return l2;
if(l2 == null)
return l1;
if(l1 == null && l2 == null)
return null;
ListNode res = null;
ListNode last = res;
while(l1 != null || l2 != null){
if(l1 != null && l2 != null){
if(l1.val <= l2.val){
if(res == null){
last = l1;
res = l1;
}
else{
res.next = l1;
res = res.next;
}
l1 = l1.next;
}
else{
if(res == null){
last = l2;
res = l2;
} else{
res.next = l2;
res = res.next;
}
l2 = l2.next;
}
}
else if(l1 != null ){
res.next = l1;
res = res.next;
l1 = l1.next;
}
else if(l2 != null ){
res.next = l2;
res = res.next;
l2 = l2.next;
}
}
return last;
}
}