【leetcode】 21. Merge Two Sorted Lists

题目描述：

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.

解题分析：

再基础不过的题了，直接看代码吧^-^

具体代码：

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
public class Solution {
    public static ListNode mergeTwoLists(ListNode head1, ListNode head2) {
        if(head1==null)
            return head2;
        if(head2==null)
            return head1;
        ListNode head=null;
        ListNode current=null;
        if(head1.val<=head2.val){
            head=head1;
            head1=head1.next;
            head.next=null;
        }
        else{
            head=head2;
            head2=head2.next;
            head.next=null;
        }
        current=head;
        while(head1!=null&&head2!=null){
            if(head1.val<=head2.val){
                current.next=head1;
                current=current.next;
                head1=head1.next;
                current.next=null;
            }
            else{
                current.next=head2;
                current=current.next;
                head2=head2.next;
                current.next=null;
            }
        }
        if(head1!=null){
            current.next=head1;
        }
        if(head2!=null){
            current.next=head2;
        }
        return head;
    }
}