LeetCode Database: Consecutive Numbers

Write a SQL query to find all numbers that appear at least three times consecutively.

+----+-----+
| Id | Num |
+----+-----+
| 1  |  1  |
| 2  |  1  |
| 3  |  1  |
| 4  |  2  |
| 5  |  1  |
| 6  |  2  |
| 7  |  2  |
+----+-----+

For example, given the above Logs table, 1 is the only number that appears consecutively for at least three times.

# Write your MySQL query statement below
SELECT DISTINCT Num FROM (
    SELECT    Num,
              @cnt := IF(@prevNum = Num, @cnt, 0),
              @cnt := @cnt + 1 as Cnt,
              @prevNum := Num
    FROM      Logs s, (SELECT @cnt := 0) r, (SELECT @prevNum := NULL) p
    ORDER BY  Id ASC
  ) t where Cnt >= 3 ;