Merge Two Sorted Lists

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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.

解题思路
对比两个表头的元素，将较小者插入新的链表中。

源代码

package leetcode;/*private class ListNode {     int val;     ListNode next;     ListNode(int x) {         val = x;         next = null;     }}*/public class MergeTwoSortedLists {public ListNode mergeTwoLists(ListNode l1, ListNode l2) {//处理空串的情形if(l1 == null) return l2;if(l2 == null) return l1;ListNode result = null;ListNode lastNode = null;if(l1.val <= l2.val){lastNode = new ListNode(l1.val);l1 = l1.next;}else{lastNode = new ListNode(l2.val);l2 = l2.next;}result = lastNode;while(l1 != null && l2 != null){ListNode newNode = null;if(l1.val <= l2.val){newNode = new ListNode(l1.val);l1 = l1.next;}else{newNode = new ListNode(l2.val);l2 = l2.next;}lastNode.next = newNode;lastNode = newNode;}if(l1 == null)lastNode.next = l2;if(l2 == null)lastNode.next = l1;        return result;    }public static void main(String[] args) {ListNode node1 = new ListNode(1); ListNode node2 = new ListNode(2);ListNode node3 = new ListNode(3);ListNode node4 = new ListNode(4);ListNode node5 = new ListNode(5);ListNode node6 = new ListNode(6);ListNode node7 = new ListNode(1); ListNode node8 = new ListNode(2);ListNode node9 = new ListNode(3);ListNode node10 = new ListNode(4);ListNode node11 = new ListNode(5);ListNode node12 = new ListNode(6);node1.next = node2;node2.next = node3;node3.next = node4;node4.next = node5;node5.next = node6;node7.next = node8;node8.next = node9;node9.next = node10;node10.next = node11;node11.next = node12;ListNode l1 = node1;//System.out.println(l1.val);ListNode l2 = node7;//System.out.println(l2.val);MergeTwoSortedLists mtsl = new MergeTwoSortedLists();ListNode result = mtsl.mergeTwoLists(l1, l2);while(result != null){System.out.print(result.val + " ");result = result.next;}}}

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