【LeeCode】21. 合并两个有序链表

【题目描述】

将两个升序链表合并为一个新的 升序 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。 

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【示例】

【代码】

package com.company;

class ListNode {
    int val;
    ListNode next;

    ListNode() { }
    ListNode(int val) { this.val = val; }
    ListNode(int val,ListNode next) { this.val = val; this.next = next; }

    public void setNext(ListNode next) {
        this.next = next;
    }

    public void setVal(int val) {
        this.val = val;
    }

    public int getVal() {
        return val;
    }

    public ListNode getNext() {
        return next;
    }

    @Override
    public String toString() {
        return "ListNode{" +
                "val=" + val +
                ", next=" + next +
                '}';
    }
}

public class Solution {
    public static void main(String[] args) {
        ListNode l1 = new ListNode(1);
        ListNode l2 = new ListNode(2);
        ListNode l3 = new ListNode(4);
        l1.setNext(l2);
        l2.setNext(l3);


        ListNode l4 = new ListNode(1);
        ListNode l5 = new ListNode(3);
        ListNode l6 = new ListNode(4);

        l4.setNext(l5);;
        l5.setNext(l6);

        System.out.println(l1.toString());
        System.out.println(l4.toString());
        ListNode listNode = mergeTwoLists(l1, l4);
        System.out.println(listNode.toString());

    }

    public static ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        if (l1 == null || l2 == null){
            return (l1 == null) ? l2 : l1;
        }else if (l1.val <= l2.val){
            l1.next = mergeTwoLists(l1.next, l2);
            return l1;
        }else{
            l2.next = mergeTwoLists(l1, l2.next);
            return l2;
        }
    }
}

​​学习参考​​

​​https://leetcode.cn/problems/merge-two-sorted-lists/solutions/​​