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String Run-Length Encoding
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String Run-Length Encoding

HardPython

Problem

Given a string, how would you write a function that returns each character with its consecutive count, like aaaaffffggaa -> a4f4g2a2?

Return one character-count pair for each maximal consecutive run, preserving the original order. The function should return an empty string for empty input and treat characters as case-sensitive.

def encode_runs(s): accepts a string and returns a string.

Constraints

  • 0 <= len(s) <= 100000
  • s contains Unicode characters supported by Python strings
  • Character comparison is case-sensitive
  • Counts may contain multiple digits

Function Signature

def encode_runs(s):
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