21. 合并两个有序链表
21. Merge Two Sorted Lists
题目描述
将两个有序链表合并为一个新的有序链表并返回。新链表是通过拼接给定的两个链表的所有节点组成的。
LeetCode21. Merge Two Sorted Lists
示例:
Java 实现
ListNode 类
class ListNode {
int val;
ListNode next = null;
ListNode(int val) {
this.val = val;
}
@Override
public String toString() {
return val + "->" + next;
}
}Iterative Solution
public class Solution {
public ListNode mergeTwoLists(ListNode list1, ListNode list2) {
if (list1 == null && list2 == null) {
return null;
}
if (list1 == null) {
return list2;
}
if (list2 == null) {
return list1;
}
ListNode head = new ListNode(-1);
ListNode curr = head;
while (list1 != null && list2 != null) {
if (list1.val <= list2.val) {
curr.next = list1;
list1 = list1.next;
} else {
curr.next = list2;
list2 = list2.next;
}
curr = curr.next;
}
if (list1 != null) {
curr.next = list1;
}
if (list2 != null) {
curr.next = list2;
}
return head.next;
}
}Recursive Solution
public class Solution {
public ListNode mergeTwoLists(ListNode list1, ListNode list2) {
if (list1 == null) {
return list2;
}
if (list2 == null) {
return list1;
}
if (list1.val <= list2.val) {
list1.next = mergeTwoLists(list1.next, list2);
return list1;
} else {
list2.next = mergeTwoLists(list1, list2.next);
return list2;
}
}
}相似题目
参考资料
LeetCode 21. 合并两个有序链表(Merge Two Sorted Lists)
原文：https://www.cnblogs.com/hglibin/p/10897016.html