Simple numeric reconstruction
Input
[(1, 3), (2, 1)]
Output
[1, 1, 1, 2]
1 repeated 3 times, then 2 repeated once.
Full lesson preview
Reconstruct a list from value-count tuples
Build a flattened list by repeating values according to provided counts.
Python practice25 minLists & TuplesAdvancedLast updated March 17, 2026
Problem statement
Write a function reconstruct(pairs) that takes a list of tuples pairs where each tuple is (value, count). Return a single list containing each value repeated count times, preserving the order of tuples. You may assume count is a non-negative integer. If pairs is empty, return an empty list.
Task
Given a list of (value, count) tuples, return a list where each value appears count times in order.
Examples
Input format
A single argument: a list of (value, count) tuples. count is a non-negative integer.
Output format
Return a list with values repeated according to their counts.
Constraints
Do not import external libraries. Counts are non-negative integers; handle zero by producing no occurrences of that value. Maintain the input order.
Samples
Sample 1
Input
[('a', 2), ('b', 0), ('a', 1)]
Output
['a', 'a', 'a']
First 'a' twice, then 'b' zero times (skipped), then 'a' once more.