Consecutive Available Seats

Problem

Table: Cinema

+-------------+------+
| Column Name | Type |
+-------------+------+
| seat_id     | int  |
| free        | bool |
+-------------+------+
seat_id is an auto-increment column for this table.
Each row of this table indicates whether the ith seat is free or not. 1 means free while 0 means occupied.

Find all the consecutive available seats in the cinema.

Return the result table ordered by seat_id in ascending order.

The test cases are generated so that more than two seats are consecutively available.

The result format is in the following example.

Examples

Example 1

Input: 
Cinema table:
+---------+------+
| seat_id | free |
+---------+------+
| 1       | 1    |
| 2       | 0    |
| 3       | 1    |
| 4       | 1    |
| 5       | 1    |
+---------+------+
Output: 
+---------+
| seat_id |
+---------+
| 3       |
| 4       |
| 5       |
+---------+

Solution

Method 1 - using where clause

Code

Sql

select c1.seat_id
from cinema c1, cinema c2
where ((c1.seat_id = c2.seat_id+1) or
       (c1.seat_id = c2.seat_id-1)) and 
    (c1.free = 1) and (c2.free = 1)
group by c1.seat_id