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Advent of Code 2021

Info and problems are available at https://adventofcode.com/2021

Overview

Each day's problem input and solution is in a subdirectory, 01, 02, etc.

Solutions are mostly C++: problem 1 is doit1.cc, problem 2 is doit2.cc. Compile with

g++ -Wall -g -o doit1 doit1.cc

Input is on stdin, output is printed to stdout.

Input has sometimes been pre-processed for ease of reading. Example input if any is called input1. The real input is input (note, my inputs are no longer included in the repository).

Sometimes I might go back and revisit a problem in a different (usually more efficient) way. doit2a.cc would be an alternative to doit2.cc.

Occasionally there's only one program used for both parts.

Recommended problems

Here's my list of recommended problems for the year, along with direct links. Recommendations are based on a combination of factors: perhaps the problem admits an unusual and clever solution, or perhaps it would allow an interesting visualization, or perhaps the problem description itself was cute. In whatever way, I found the problem unusually fun. Each of these problems is either ⭐ (recommended) or ⭐⭐ (highly recommended).

Advent calendar for 2021