Is Consecutive Numbers easy or hard?

Consecutive Numbers is generally considered a medium-level problem because the logic is simple but requires recognizing that only adjacent comparisons matter. Once you identify the sliding window pattern, the implementation becomes straightforward.

How to solve Consecutive Numbers in O(n)?

Iterate through the ordered numbers and check whether the current value matches the previous two values. If nums[i] == nums[i-1] and nums[i] == nums[i-2], record that number as a valid result. This linear scan ensures O(n) time complexity.

What is the best approach for Consecutive Numbers?

The most efficient approach is a sliding window that checks three adjacent records at a time. By comparing nums[i], nums[i-1], and nums[i-2], you can detect consecutive duplicates in a single pass. This runs in O(n) time and O(1) space.

What data structure is used in Consecutive Numbers?

The simplest solution uses direct array traversal with a fixed-size sliding window. An alternative implementation uses a hash map or dictionary to track consecutive streak counts for numbers while iterating.

What is the time complexity of Consecutive Numbers?

The optimal solution runs in O(n) time because it scans the dataset once while comparing neighboring values. Space complexity is O(1) for the sliding window approach, since only a few variables are needed during traversal.

Consecutive Numbers Python or Java solution approach?

In Python or Java, iterate through the array and compare the current element with the two previous elements. If all three match, add the value to the result set. The implementation uses simple loops and conditional checks, giving O(n) time complexity.

Is Consecutive Numbers asked at Google, Amazon, or Meta?

Consecutive sequence detection problems appear frequently in database and data-processing interview rounds at companies like Amazon and Meta. Variations often involve detecting streaks, repeated events, or consecutive records in logs.

Description Solution Video 5:27

180. Consecutive Numbers

Medium49.7% acceptance9 companies

Table: Logs

+-------------+---------+
| Column Name | Type    |
+-------------+---------+
| id          | int     |
| num         | varchar |
+-------------+---------+
In SQL, id is the primary key for this table.
id is an autoincrement column starting from 1.

Find all numbers that appear at least three times consecutively.

Return the result table in any order.

The result format is in the following example.

Example 1:

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.

Asked at 9 companies

Accenture Delhivery Meesho

TCS

Google Amazon Bloomberg Microsoft Meta

Topics

Database

5:27

Still stuck?Read 5 approaches, or watch a walkthrough.

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1# Write your MySQL query statement below

Starter codeMySQLSpaces: 4

Examples

Case 1

Input

{"headers":{"Logs":["id","num"]},"rows":{"Logs":[[1,1],[2,1],[3,1],[4,2],[5,1],[6,2],[7,2]]}}

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