Day02

力扣

select FirstName, LastName, City, State
from Person as p
left join Address as a
on p.PersonId = a.PersonId;

City和State位于Address表中，利用左连接将表连接起来！

力扣

/**
 * 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) {

        //创建一个头结点
        ListNode head=new ListNode(0);
        head.next=list1;
        ListNode temp1=head,temp2=head;
        //第一个指针迭代到索引为a-1处
        for(int i=1;i<=a;i++){
            temp1=temp1.next;
        }
        //第二个指针迭代到索引为b+1处
        for(int i=1;i<=b+2;i++){
            temp2=temp2.next;
        }
        //被插入的链表指针移到末尾
        ListNode list3=list2;
        while(list3.next!=null){
            list3=list3.next;
        }
        //插入
        temp1.next=list2;
        list3.next=temp2;
        return head.next;
    }
}