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.
For grins, I compiled yours on my little laptop, got 3.027
seconds runtime, then did the obvious conversion to a simple 2D
array, which runs in 0.019 seconds.
Andy
```d
#!/usr/bin/env rdmd
import std.algorithm;
import std.conv;
import std.file;
import std.stdio;
import std.string;
const MAX_X = 1_000;
const MAX_Y = 1_000;
alias Dvals = ubyte[MAX_X][MAX_Y];
enum Option
{
off = 0,
on = 1,
toggle = 2
}
private void
extract_pair(const string s, out size_t x, out size_t y)
{
auto parts = s.split(",");
x = parts[0].to!int;
y = parts[1].to!int;
}
void process_line(ref Dvals d, in string line)
{
auto parts = line.split();
Option option;
// dfmt off
if (parts[1] == "on") {
option = Option.on;
} else if (parts[1] == "off") {
option = Option.off;
} else if (parts[0] == "toggle") {
option = Option.toggle;
} else {
assert(0);
}
// dfmt on
size_t x1, y1, x2, y2;
if (option == Option.on || option == Option.off)
{
extract_pair(parts[2], x1, y1);
extract_pair(parts[$ - 1], x2, y2);
const ubyte val = (option == Option.on) ? 1 : 0;
for (size_t i = x1; i <= x2; ++i)
{
for (size_t j = y1; j <= y2; ++j)
{
d[i][j] = val; // off: 0, on: 1
}
}
}
else if (option == Option.toggle)
{
extract_pair(parts[1], x1, y1);
extract_pair(parts[$ - 1], x2, y2);
for (size_t i = x1; i <= x2; ++i)
{
for (size_t j = y1; j <= y2; ++j)
{
d[i][j] ^= 1;
}
}
}
else
{
assert(0);
}
}
auto
get_result(in Dvals d)
{
// if value is 0: off, 1: on
uint res = 0;
foreach(x; 0 .. MAX_X) {
foreach(y; 0 .. MAX_Y) {
res += d[x][y];
}
}
return res;
}
void main()
{
// const fname = "example1.txt";
// const fname = "example2.txt";
// const fname = "example3.txt";
const fname = "input.txt";
const lines = readText(fname).splitLines;
Dvals d;
foreach (line; lines)
{
process_line(d, line);
}
int result = get_result(d);
writeln(result);
}
```
