标签：style blog class code java tar
一点小错，两次过，基本思想是先比较头元素，哪个小就在哪个list的基础上插入，需要考虑两种不同的结束方式
1 /** 2 * Definition for singly-linked list. 3 * public class ListNode { 4 * int val; 5 * ListNode next; 6 * ListNode(int x) { 7 * val = x; 8 * next = null; 9 * } 10 * } 11 */ 12 public class Solution { 13 public ListNode mergeTwoLists(ListNode l1, ListNode l2) { 14 if(l1 == null && l2 !=null) return l2; 15 if(l2 == null && l1 !=null) return l1; 16 if(l1 == null && l2 ==null) return null; 17 ListNode head1, head2, tail1, tail2; 18 if (l1.val < l2.val){ 19 head1 = l1; 20 head2 = l2; 21 } 22 else { 23 head1 = l2; 24 head2 = l1; 25 } 26 tail1 = head1; 27 tail2 = head2; 28 while (tail1.next != null && tail2 != null){ 29 if (tail1.next.val > tail2.val){ 30 ListNode n = new ListNode(tail2.val); 31 n.next = tail1.next; 32 tail1.next = n; 33 tail1 = tail1.next; 34 tail2 = tail2.next; 35 } 36 else { 37 tail1 = tail1.next; 38 } 39 } 40 41 if (tail1.next == null){ // end case1: tail1 reaches end before tail2 42 while (tail2 != null){ 43 ListNode n = new ListNode(tail2.val); 44 tail1.next = n; 45 tail1 = tail1.next; 46 tail2 = tail2.next; 47 } 48 } 49 50 //end case2: tail2 reaches end before tail1, no need to process 51 52 return head1; 53 } 54 }
别人的另外一种思路是，重新创建一个新的Linkedlist，把两个list的元素往里面插入，有很多细节很聪明，比如，第一个node建立为一个假的，ListNode dummyNode=new ListNode(Integer.MIN_VALUE), 最后返回dummyNode.next; 每次不new一个新的ListNode, 而是用已有的。
1 /** 2 * Definition for singly-linked list. 3 * public class ListNode { 4 * int val; 5 * ListNode next; 6 * ListNode(int x) { 7 * val = x; 8 * next = null; 9 * } 10 * } 11 */ 12 public class Solution { 13 public ListNode mergeTwoLists(ListNode l1, ListNode l2) { 14 // Start typing your Java solution below 15 // DO NOT write main() function 16 17 ListNode dummyNode = new ListNode(0); 18 ListNode currentNode = dummyNode; 19 20 while(l1!=null||l2!=null){ 21 if(l1!=null&&l2!=null) 22 if(l1.val>l2.val){ 23 currentNode.next =l2; 24 l2 = l2.next; 25 }else{ 26 currentNode.next =l1; 27 l1 = l1.next; 28 } 29 else if(l1==null){ 30 currentNode.next =l2; 31 l2 = l2.next; 32 }else{ 33 currentNode.next =l1; 34 l1 = l1.next; 35 } 36 currentNode=currentNode.next; 37 38 } 39 return dummyNode.next; 40 41 } 42 }
Leetcode: Merge Two Sorted Lists,布布扣,bubuko.com
Leetcode: Merge Two Sorted Lists
标签：style blog class code java tar
原文地址：http://www.cnblogs.com/EdwardLiu/p/3718025.html
