Modern C++ in Advent of Code: Day 5

On the fifth day of Advent Of Code, we are tasked to simulate a crane reordering crates.

I recommend you try to solve the problems yourself: https://adventofcode.com.

Input

The main complexity of today's problem is input parsing, so for the first time, let’s look at the parsing code. For simple processing, it would be convenient to have the state represented as std::vector<std::vector<char>>.

The input is inconveniently irregular with significant whitespace. The simplest way to parse such input in C++ is first to parse by-line and then interpret each line.

Unlike the initial state, the orders are regular, so we can introduce a custom type and overload the stream extraction operator.

Part1: CrateMover 9000

For part one, we can now process each order, modifying the state as we go.

We could move crates one by one; however, we can also move all crates with one std::ranges::copy, which is arguably simpler. Either way, we must remember to remove the crates from the source.

Part2: CrateMover 9001

For part two, we can re-use the same code, with the caveat that now we copy the crates in order.

Links

The repository with a complete solution (including input parsing) is available here: https://github.com/HappyCerberus/moderncpp-aoc-2022.

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