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Finish day02, part 2

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ktkk 2025-12-02 20:19:23 +00:00
parent 34f9fff423
commit ee219fc9b2
1 changed files with 49 additions and 42 deletions
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91
src/days/day02.zig
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@ -3,58 +3,25 @@ const std = @import("std");
pub const title = "Day 02"; pub const title = "Day 02";
pub fn run(_: std.mem.Allocator) !void { pub fn run(_: std.mem.Allocator) !void {
const input = @embedFile("./input/day02.txt"); const input = std.mem.trim(u8, @embedFile("./input/day02.txt"), &std.ascii.whitespace);
//const input =
// \\11-22,95-115,998-1012,1188511880-1188511890,222220-222224,1698522-1698528,446443-446449,38593856-38593862,565653-565659,824824821-824824827,2121212118-2121212124
// ;
var ranges = std.mem.tokenizeScalar(u8, input, ','); var ranges = std.mem.tokenizeScalar(u8, input, ',');
var accumulator: u64 = 0; var accumulator: u64 = 0;
while (ranges.next()) |range| { while (ranges.next()) |range| {
var components = std.mem.tokenizeScalar(u8, range, '-'); var components = std.mem.tokenizeScalar(u8, range, '-');
const start_s = std.mem.trim(u8, components.next() orelse continue, &std.ascii.whitespace);
const end_s = std.mem.trim(u8, components.next() orelse continue, &std.ascii.whitespace); const start_s = components.next() orelse continue;
const end_s = components.next() orelse continue;
const start = try std.fmt.parseUnsigned(u64, start_s, 10); const start = try std.fmt.parseUnsigned(u64, start_s, 10);
const end = try std.fmt.parseUnsigned(u64, end_s, 10); const end = try std.fmt.parseUnsigned(u64, end_s, 10);
std.debug.print("{d} to {d}\n", .{start, end}); std.debug.print("{d} to {d}\n", .{start, end});
try processRange(&accumulator, start, end);
for (start..end+1) |id| {
std.debug.print("-- Checking {d} --\n", .{id});
// IDs smaller than 10 cannot possibly have repeated digits
if (id / 10 == 0) {
std.debug.print("Skipping {d}\n", .{id});
continue;
}
const len = getLen(id);
inner: for (2..len + 1) |divisor| {
if (len % divisor != 0) continue;
std.debug.print("divisor = {d}\n", .{divisor});
const window_len = len / divisor;
std.debug.print("window_len = {d}\n", .{window_len});
for (0..window_len) |i| {
const a = getDigit(id, i);
std.debug.print("a = {d}\n", .{a});
for (1..divisor) |n| {
const b = getDigit(id, i + window_len * n);
std.debug.print("b = {d}\n", .{b});
if (a != b) {
continue :inner;
}
}
}
// If we get here, it means id is a valid cadidate
std.debug.print("result = {d}\n", .{id});
break;
}
accumulator += id;
}
break;
} }
var buffer: [64]u8 = undefined; var buffer: [64]u8 = undefined;
@ -66,6 +33,46 @@ pub fn run(_: std.mem.Allocator) !void {
try stdout.flush(); try stdout.flush();
} }
fn processRange(accumulator: *u64, start: u64, end: u64) !void {
for (start..end+1) |id| {
std.debug.print("-- Checking {d} --\n", .{id});
// IDs smaller than 10 cannot possibly have repeated digits
if (id / 10 == 0) {
std.debug.print("Skipping {d}\n", .{id});
continue;
}
const len = getLen(id);
inner: for (2..len + 1) |divisor| {
if (len % divisor != 0) continue;
std.debug.print("divisor = {d}\n", .{divisor});
const offset = len / divisor;
std.debug.print("offset = {d}\n", .{offset});
for (0..offset) |i| {
const a = getDigit(id, i);
std.debug.print("a = {d}\n", .{a});
for (1..divisor) |n| {
const b = getDigit(id, i + offset * n);
std.debug.print("b = {d}\n", .{b});
if (a != b) {
continue :inner;
}
}
}
// If we get here, it means id is a valid cadidate
std.debug.print("result = {d}\n", .{id});
accumulator.* += id;
break;
}
}
}
fn getDigit(x: u64, n: usize) u8 { fn getDigit(x: u64, n: usize) u8 {
var new_x = x; var new_x = x;
for (0..n) |_| { for (0..n) |_| {