On Monday, 24 November 2025 at 14:37:22 UTC, Jabba Laci wrote:
I implemented [Advent of Code 2015, Day 6, Part
1](https://adventofcode.com/2015/day/6) in D. The code is here:
https://github.com/jabbalaci/AdventOfCode2015/tree/main/day06/d/part1 . It runs for 3 seconds. I found it a bit much, so I also wrote it in Python. To my surprise, the Python program also ran for 3 seconds. I expected that the D program should be much faster.
I made it faster. Compile it with `dub build --compiler=ldc2
--build=release`:
```d
#!/usr/bin/env rdmd
import std.algorithm;
import std.conv;
import std.file;
import std.stdio;
import std.string;
import std.typecons;
alias Pair = Tuple!(int, int);
enum Option
{
off = 0,
on = 1,
toggle = 2
}
Pair extract_pair(const string s)
{
// NOTE(Kap): No idea, just did it this way because it seems
better to me.
foreach (i, c; s)
{
if (c != ',') continue;
return tuple(s[0 .. i].to!int, s[i + 1 .. $].to!int);
}
return tuple(0, 0);
}
void process_line(ref int[1000][] d, const string line)
{
// NOTE(Kap): No idea, was thining that split was slow or
something, but maybe not.
string[16] parts_buffer;
string[] parts;
{
size_t part_index, previous_space_index;
foreach (i, c; line) {
if (c != ' ') continue;
parts_buffer[part_index] = line[previous_space_index
.. i];
previous_space_index = i + 1;
part_index += 1;
}
parts_buffer[part_index] = line[previous_space_index ..
$];
parts = parts_buffer[0 .. part_index + 1];
}
Option option;
// dfmt off
// NOTE(Kap): I'm trying to be smart here for no reason.
if (parts[1][$ - 1] == 'n') {
option = Option.on;
} else if (parts[1][$ - 1] == 'f') {
option = Option.off;
} else if (parts[0][$ - 1] == 'e') {
option = Option.toggle;
} else {
assert(0);
}
// dfmt on
if (option == Option.on || option == Option.off)
{
auto pair1 = extract_pair(parts[2]);
auto pair2 = extract_pair(parts[$ - 1]);
int x1 = pair1[0], y1 = pair1[1];
int x2 = pair2[0], y2 = pair2[1];
for (int i = x1; i <= x2; ++i)
{
for (int j = y1; j <= y2; ++j)
{
d[i][j] = int(option); // off: 0, on: 1
}
}
}
else if (option == Option.toggle)
{
auto pair1 = extract_pair(parts[1]);
auto pair2 = extract_pair(parts[$ - 1]);
int x1 = pair1[0], y1 = pair1[1];
int x2 = pair2[0], y2 = pair2[1];
for (int i = x1; i <= x2; ++i)
{
for (int j = y1; j <= y2; ++j)
{
d[i][j] = 1 - d[i][j];
}
}
}
else
{
assert(0);
}
}
int get_result(int[1000][] d)
{
// if value is 0: off, 1: on
auto result = 0;
foreach (ref col; d) foreach (x; col) result += x;
return result;
}
void main()
{
// const fname = "example1.txt";
// const fname = "example2.txt";
// const fname = "example3.txt";
const fname = "input.txt";
const lines = readText(fname).splitLines;
// int[Pair] d;
auto d = new int[1000][1000];
foreach (line; lines)
{
process_line(d, line);
}
int result = get_result(d);
writeln(result);
}
```
