https://oj.leetcode.com/problems/merge-two-sorted-lists/
http://blog.csdn.net/linhuanmars/article/details/19712593
/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) {
* val = x;
* next = null;
* }
* }
*/
public class Solution {
public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
if (l1 == null && l2 == null)
return null;
ListNode toReturn = null;
ListNode curNode = null;
ListNode lastNode = null;
while (l1 != null || l2 != null)
{
// Select current node;
if (l1 == null)
{
curNode = l2;
l2 = l2.next;
}
else if (l2 == null)
{
curNode = l1;
l1 = l1.next;
}
else if (l1.val < l2.val)
{
curNode = l1;
l1 = l1.next;
}
else
{
curNode = l2;
l2 = l2.next;
}
if (toReturn == null)
toReturn = curNode;
if (lastNode != null)
lastNode.next = curNode;
lastNode = curNode;
}
return toReturn;
}
}[LeetCode]21 Merge Two Sorted Lists
原文：http://7371901.blog.51cto.com/7361901/1598855