【每日一题Day103】LC1669合并两个链表

【每日一题Day103】LC1669合并两个链表 | 模拟

news2024/9/26 1:23:39

合并两个链表【LC1669】

You are given two linked lists: list1 and list2 of sizes n and m respectively.

Remove list1’s nodes from the ath node to the bth node, and put list2 in their place.

The blue edges and nodes in the following figure indicate the result:

Build the result list and return its head.

思路：遍历链表找到list1中的第 $a - 1$ 个节点和第 $b + 1$ 个节点，然后将第 $a - 1$ 个节点指向list2链表的初始节点，list2链表的尾节点指向list1中的第 $b + 1$ 个节点

实现

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode mergeInBetween(ListNode list1, int a, int b, ListNode list2) {
        ListNode dummyNode = new ListNode(-1, list1);
        ListNode pre = dummyNode;
        ListNode cur = dummyNode.next;
        int idx = 0;
        while (idx != a){
            pre = cur;
            cur = cur.next;  
            idx++;          
        }
        while (idx != b){
            cur = cur.next;
            idx++;
        }
        pre.next = list2;
        while (list2.next != null){
            list2 = list2.next;
        }

        list2.next = cur.next;
        cur.next = null;
        return list1;       
    }
}