Problem 40. Reverse Run-Length Encoder

Created by MathWorks Cody Team

Solve Later

Given a "counting sequence" vector x, construct the original sequence y.

A counting sequence is formed by "counting" the entries in a given sequence. This is sometimes called run-length encoding.

For example, the sequence

 x = 2, 5, 1, 2, 4, 1, 1, 3

can be read as

 Two 5's, one 2, four 1's, one 3

which translates to

 y = 5, 5, 2, 1, 1, 1, 1, 3

So y is the reconstructed vector that corresponds to the counting sequence x.

For this problem, all elements in the sequences x and y will be in the range from 1 to 9.

Solve

Solution Stats

3990 Solutions
2715 Solvers

Last Solution submitted on Jan 14, 2026

Last 200 Solutions

Problem Comments

5 Comments

5 Comments

Show 2 older comments

Carl Witthoft on 17 Nov 2015

See my function "seqle" on FileExchange. It may not be as compact, but it's easy to use and both encodes and decodes.

David Verrelli on 28 Sep 2017

The problem statement would have been clearer if the principle of RLE had been explained with an encoding example first. Alternatively, it would have been useful to explicitly mention that the data in vector x is being read pairwise.

Sanzhar Askaruly on 5 Jul 2019

easy

subbarao satha on 2 Mar 2020

useful challenge

赛鼎薛华 on 11 Jul 2022

useful

Solution Comments

Show comments

Problem Recent Solvers2715

Problem Tags

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Problem 40. Reverse Run-Length Encoder

Solution Stats

Last 200 Solutions

Problem Comments

Solution Comments

Problem Recent Solvers2715

Suggested Problems

More from this Author96

Problem Tags

Community Treasure Hunt

Problem 40. Reverse Run-Length Encoder

Solution Stats

Last 200 Solutions

Problem Comments

Solution Comments

Problem Recent Solvers2715

Suggested Problems

More from this Author96

Problem Tags

Community Treasure Hunt

Players