Merge Two Sorted Lists

归并两个有序序列为一个有序序列

Merge Two Sorted Lists

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.

/**
 * 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) {
        ListNode i = l1;
        ListNode j = l2;
        ListNode k ;
        ListNode end;
        //有空序列
        if(null == l1 && null ==l2)
            return null;
        else if(null == l1 || null == l2){
            return null == l1 ? l2:l1; 
        }
        //没有空序列
        if(i.val < j.val){
            k = new ListNode(i.val);
            k.next = null;
            i = i.next;
        }else
        {
            k = new ListNode(j.val);
            k.next = null;
            j = j.next;
        }
        end = k;
        
        while(null != i && null != j){
            ListNode temp;
            if(i.val < j.val){
                temp = new ListNode(i.val);
                
                i = i.next;
            }else{
                temp =  new ListNode(j.val);
                j = j.next;
            }
            temp.next = null;
            end.next = temp;
            end = temp;
        }
        if(null != i){
            while(null != i){
                ListNode temp = new ListNode(i.val);
                temp.next = null;
                end.next = temp;
                end = temp;
                i = i.next;
            }
        }
        if(null != j){
            while(null != j){
                ListNode temp = new ListNode(j.val);
                temp.next = null;
                end.next = temp;
                end = temp;
                j = j.next;
            }
        }
        
        return k;
    }
}