Advanced List Sort

Challenge Difficulty: Medium | Estimated completion time: ~20 minutes

Create a function that takes a list of numbers or strings and returns a list with the items from the original list stored into sub lists. Items of the same value should be in the same sub list.

Examples

advanced_sort([2, 1, 2, 1]) ➞ [[2, 2], [1, 1]]
 
advanced_sort([5, 4, 5, 5, 4, 3]) ➞ [[5, 5, 5], [4, 4], [3]]
 
advanced_sort(["b", "a", "b", "a", "c"]) ➞ [["b", "b"], ["a", "a"], ["c"]]

Notes

The sub lists should be returned in the order of each element’s first appearance in the given list.

Solution

Python

from typing import Any def advanced_sort(items: list[Any]) -> list[list[Any]]: """Group items by value, preserving first appearance order. Args: items: List of numbers or strings Returns: List of sublists where each sublist contains items of the same value """ seen_order: list[Any] = [] groups: dict[Any, list[Any]] = {} for item in items: if item not in groups: seen_order.append(item) groups[item] = [] groups[item].append(item) return [groups[key] for key in seen_order] if __name__ == "__main__": print(advanced_sort([2, 1, 2, 1])) # [[2, 2], [1, 1]] print(advanced_sort([5, 4, 5, 5, 4, 3])) # [[5, 5, 5], [4, 4], [3]] print(advanced_sort(["b", "a", "b", "a", "c"])) # [["b", "b"], ["a", "a"], ["c"]]

Output