链接
题目描述
1.迭代
代码
/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) { val = x; }
* }
*/
class Solution {
public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
if(l1 == null){
return l2;
}
if(l2 == null){
return l1;
}
ListNode dummy = new ListNode(0);
ListNode p = dummy;
ListNode p1 = l1;
ListNode p2 = l2;
while(l1 != null && l2 != null){
if(l1.val < l2.val){
p.next = l1;
l1 = l1.next;
p = p.next;
}else{
p.next = l2;
l2 = l2.next;
p = p.next;
}
}
p.next = l1 == null ? l2 : l1;
return dummy.next;
}
}
2.递归
代码
/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) { val = x; }
* }
*/
class Solution {
public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
//递归
if(l1 == null){
return l2;
}
if(l2 == null){
return l1;
}
if(l1.val < l2.val){
l1.next = mergeTwoLists(l1.next,l2);
return l1;
}else{
l2.next = mergeTwoLists(l1,l2.next);
return l2;
}
}
}