Merge Two Sorted Lists_Leetcode_#21

1.题目

Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.

2.解法

/**
* Definition for singly-linked list.
* public class ListNode {
*     int val;
*     ListNode next;
*     ListNode(int x) { val = x; }
* }
*/
public class Solution {
public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
ListNode pNode = null;
ListNode pHead = null;
if(l1 == null){
return l2;
}else if(l2 == null){
return l1;
}else{
if(l1.val <= l2.val){
pNode = l1;
l1 = l1.next;
}else{
pNode = l2;
l2 = l2.next;
}
pHead = pNode;
while(l1 != null && l2 != null){
if(l1.val <= l2.val){
pNode.next = l1;
l1 = l1.next;
pNode = pNode.next;
}else{
pNode.next = l2;
l2 = l2.next;
pNode = pNode.next;
}
}
if(l1 != null){
pNode.next = l1;
}
if(l2 != null){
pNode.next = l2;
}
}

return pHead;
}
}