leetcode - 1225. Report Contiguous Dates

난이도 : Hard

 

Table: Failed

+--------------+---------+
| Column Name  | Type    |
+--------------+---------+
| fail_date    | date    |
+--------------+---------+
fail_date is the primary key for this table.
This table contains the days of failed tasks.

 

Table: Succeeded

+--------------+---------+
| Column Name  | Type    |
+--------------+---------+
| success_date | date    |
+--------------+---------+
success_date is the primary key for this table.
This table contains the days of succeeded tasks.

 

A system is running one task every day. Every task is independent of the previous tasks. The tasks can fail or succeed.

Write an SQL query to generate a report of period_state for each continuous interval of days in the period from 2019-01-01 to 2019-12-31.

period_state is 'failed' if tasks in this interval failed or 'succeeded' if tasks in this interval succeeded. Interval of days are retrieved as start_date and end_date.

Return the result table ordered by start_date.

The query result format is in the following example.

 

Example 1:

Input: 
Failed table:
+-------------------+
| fail_date         |
+-------------------+
| 2018-12-28        |
| 2018-12-29        |
| 2019-01-04        |
| 2019-01-05        |
+-------------------+
Succeeded table:
+-------------------+
| success_date      |
+-------------------+
| 2018-12-30        |
| 2018-12-31        |
| 2019-01-01        |
| 2019-01-02        |
| 2019-01-03        |
| 2019-01-06        |
+-------------------+
Output: 
+--------------+--------------+--------------+
| period_state | start_date   | end_date     |
+--------------+--------------+--------------+
| succeeded    | 2019-01-01   | 2019-01-03   |
| failed       | 2019-01-04   | 2019-01-05   |
| succeeded    | 2019-01-06   | 2019-01-06   |
+--------------+--------------+--------------+
Explanation: 
The report ignored the system state in 2018 as we care about the system in the period 2019-01-01 to 2019-12-31.
From 2019-01-01 to 2019-01-03 all tasks succeeded and the system state was "succeeded".
From 2019-01-04 to 2019-01-05 all tasks failed and the system state was "failed".
From 2019-01-06 to 2019-01-06 all tasks succeeded and the system state was "succeeded".

 

WITH sub AS (
            SELECT fail_date date
                 , "failed" period_state
                 , ROW_NUMBER() OVER (ORDER BY fail_date) rnk
            FROM Failed
            WHERE YEAR(fail_date) = 2019

            UNION ALL

            SELECT success_date date
                 , "succeeded" period_state
                 , ROW_NUMBER() OVER (ORDER BY success_date) rnk
            FROM Succeeded
            WHERE YEAR(success_date) = 2019
            )
SELECT period_state
     , MIN(date) start_date
     , MAX(date) end_date
FROM (
      SELECT *
           , DENSE_RANK() OVER (ORDER BY date) - rnk AS num
      FROM sub
      ) t
GROUP BY 1, num

Accepted (5.00%)