Message Coder

A message encoding of a given non-empty string $s$ is a dictionary $cs$ which contains, for each unique symbol in $s$ , an ordered list of the positions where that symbol occurs within $s$ .

Implement the function @coder(s)@ such that, given the message $s$ , it returns a dictionary where the keys are the unique symbols in $s$ , and the values are ordered lists containing the positions at which each symbol appears in $s$ .

Sample session

Problem information

Author: Professors Informàtica EEBE

Generation: 2026-01-25T13:39:47.610Z