面试题 25. 合并两个排序的链表
题目描述
输入两个单调递增的链表，输出两个链表合成后的链表，当然我们需要合成后的链表满足单调不减规则。
Java 实现
ListNode Class
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 Merge(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 Merge(ListNode list1, ListNode list2) {
if (list1 == null) {
return list2;
}
if (list2 == null) {
return list1;
}
if (list1.val <= list2.val) {
list1.next = Merge(list1.next, list2);
return list1;
} else {
list2.next = Merge(list1, list2.next);
return list2;
}
}
}