#0110

Run-Length Encode Values

MediumPython25 min20 XP

Problem

Given a list of values, return a list of [value, count] pairs for consecutive runs. Equal values separated later should become separate runs.

Why This Matters

Run-length encoding is a simple way to practice stateful scanning: remember the current value and how long the current run has lasted.

Function Signature

def run_length_encode(items):

Examples

Example 1

Input["a", "a", "b", "a"]

Output[["a", 2], ["b", 1], ["a", 1]]

The final "a" is a new run because it is not consecutive with the first two.

Constraints

Return the requested value exactly.
Handle the stated edge cases.
Keep the solution readable.

CodePython

def run_length_encode(items):
    """
    Input example: ["a", "a", "b", "a"]
    Return: [["a", 2], ["b", 1], ["a", 1]]
    Return the value from the function so the tests can compare it. Do not print unless the prompt asks.
    """
    # write your code here
    return []

def run_length_encode(items):
    """
    Input example: ["a", "a", "b", "a"]
    Return: [["a", 2], ["b", 1], ["a", 1]]
    Return the value from the function so the tests can compare it. Do not print unless the prompt asks.
    """
    # write your code here
    return []

Visible browser tests run here when available.

Testcases1 visible / 3 hidden categories

Core example

Input["a", "a", "b", "a"]

Expected[["a", 2], ["b", 1], ["a", 1]]

The final "a" is a new run because it is not consecutive with the first two.

Hidden Test Categories

single itemall same valuesno adjacent repeats