MediumAlgorithmsal-031

Run-Length Encoding

Problem

Encode a string by replacing each maximal run of identical characters with the character followed by the run length.

For example aaabbc encodes to a3b2c1 and a single character encodes to a1. Return the empty string for empty input.

Hint

Track a run counter and flush it whenever the character changes, including at the end.

case 1

in: ["aaabbc"]

expected: "a3b2c1"

case 2

in: [""]

expected: ""

case 3

in: ["a"]

expected: "a1"

case 4

in: ["abcd"]

expected: "a1b1c1d1"

case 5

in: ["aabbaa"]

expected: "a2b2a2"

Starter codePython

def run_length_encode(s):
    # Your code here
    pass

5 test cases · run your code against them in the editor