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Medium LC Problem = ConsecutiveNumbers.sql
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-- Table: Logs | ||
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-- +-------------+---------+ | ||
-- | Column Name | Type | | ||
-- +-------------+---------+ | ||
-- | id | int | | ||
-- | num | varchar | | ||
-- +-------------+---------+ | ||
-- In SQL, id is the primary key for this table. | ||
-- id is an autoincrement column. | ||
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-- Find all numbers that appear at least three times consecutively. | ||
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-- Return the result table in any order. | ||
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-- The result format is in the following example. | ||
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-- Example 1: | ||
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-- Input: | ||
-- Logs table: | ||
-- +----+-----+ | ||
-- | id | num | | ||
-- +----+-----+ | ||
-- | 1 | 1 | | ||
-- | 2 | 1 | | ||
-- | 3 | 1 | | ||
-- | 4 | 2 | | ||
-- | 5 | 1 | | ||
-- | 6 | 2 | | ||
-- | 7 | 2 | | ||
-- +----+-----+ | ||
-- Output: | ||
-- +-----------------+ | ||
-- | ConsecutiveNums | | ||
-- +-----------------+ | ||
-- | 1 | | ||
-- +-----------------+ | ||
-- Explanation: 1 is the only number that appears consecutively for at least three times. | ||
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-- Write your PostgreSQL query statement below | ||
-- Solution | ||
with computed_tb as ( | ||
select X.id Xid, | ||
X.num Xnum, | ||
Y.id Yid, | ||
Y.num Ynum, | ||
Y.id - X.id as diff | ||
from Logs X cross join Logs Y | ||
where Y.id - X.id in (1) and X.num = Y.num | ||
) | ||
select distinct A.Xnum as ConsecutiveNums | ||
from computed_tb A join computed_tb B on (A.Xid = B.Yid) | ||
where A.Xnum in ( | ||
select Xnum from computed_tb group by Xnum having count(Xnum) >= 2 | ||
) |