合并两个排序的链表
合并两个排序的链表
http://www.nowcoder.com/questionTerminal/d8b6b4358f774294a89de2a6ac4d9337
思路一：归并排序
public class Solution {
public ListNode Merge(ListNode list1, ListNode list2) {
if (list1 == null) {
return list2;
}
if (list2 == null) {
return list1;
}
ListNode head = new ListNode(-1);
ListNode list3 = head;
while (list1 != null && list2 != null) {
if (list1.val < list2.val) {
list3.next = list1;
list1 = list1.next;
} else {
list3.next = list2;
list2 = list2.next;
}
list3 = list3.next;
}
while (list1 != null) {
list3.next = list1;
list1 = list1.next;
list3 = list3.next;
}
while (list2 != null) {
list3.next = list2;
list2 = list2.next;
list3 = list3.next;
}
return head.next;
}
} 思路二：递归
/*
public class ListNode {
int val;
ListNode next = null;
ListNode(int val) {
this.val = val;
}
}*/
public class Solution {
public ListNode Merge(ListNode list1,ListNode list2) {
if(list1==null) return list2;
if(list2==null) return list1;
ListNode head = null;
if(list1.val<list2.val){
head = list1;
head.next=Merge(list1.next,list2);
}
else{
head = list2;
head.next=Merge(list1,list2.next);
}
return head;
}
} ----END
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