Longest Consecutive Sequence

Problem

Find the longest run of consecutive integer values in an unsorted array.

Examples

Example 1

Input: [100,4,200,1,3,2]

Output: 4

Example 2

Input: [1,2,0,1]

Output: 3

Input and output use JSON-compatible values. For linked-list and tree questions, arrays represent the node structure as described above. Your code should implement solve(input).

Write your solutionImplement solve(input). Your draft is saved in this browser.

Compiler

How to solve Longest Consecutive Sequence

Find the longest run of consecutive integer values in an unsorted array. Only start counting from a number that has no predecessor. The reference implementation illustrates this approach; check the example and edge cases.

Time and space complexity

O(n) expected time and O(n) space.

Practise and improve

Choose JavaScript, TypeScript or Python, complete the starter code, then select Run Tests. Request a hint when you need guidance, or choose View solution and confirm if you would like to study the reference implementation.