106 lines
2.8 KiB
Zig
106 lines
2.8 KiB
Zig
const std = @import("std");
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pub fn main() void {
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const input = @embedFile("input");
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var part1: usize = 0;
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// Go through each command one by one
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var iter = dirIterator.init(input);
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const root = sumSizes(&iter, 100_000, &part1);
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std.debug.print("Part 1: {}\n", .{part1});
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var part2: usize = 0;
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_ = findBiggest(iter.reset(), root - 40_000_000, &part2);
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std.debug.print("Part 2: {}\n", .{part2});
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}
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fn eql(a: []const u8, b: []const u8) bool {
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return std.mem.eql(u8, a, b);
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}
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fn findBiggest(iter: *dirIterator, minimum: usize, global: *usize) usize {
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var size: usize = 0;
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while (iter.next()) |cmd| {
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size += switch (cmd) {
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.file => iter.parseSize(),
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.dirEnter => findBiggest(iter, minimum, global),
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.dirExit => break,
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};
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}
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// If the size doesn't exceed the limit, add it to the total
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if (size > minimum and (size < global.* or global.* == 0)) global.* = size;
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// Return the size witout filtering
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return size;
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}
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fn sumSizes(iter: *dirIterator, limit: usize, total: *usize) usize {
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var size: usize = 0;
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while (iter.next()) |cmd| {
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size += switch (cmd) {
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.file => iter.parseSize(),
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.dirEnter => sumSizes(iter, limit, total),
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.dirExit => break,
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};
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}
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// If the size doesn't exceed the limit, add it to the total
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total.* += if (size <= limit) size else 0;
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// Return the size witout filtering
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return size;
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}
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// Helper to iterate through the commands
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const dirIterator = struct {
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iter: std.mem.SplitIterator(u8),
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const cmdType = enum {
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dirEnter,
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dirExit,
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file,
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};
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pub fn init(input: []const u8) dirIterator {
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return .{ .iter = std.mem.split(u8, input, "\n") };
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}
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// Returns the file size of the current line or 0
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pub fn parseSize(self: dirIterator) usize {
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const numSlice = std.mem.sliceTo(self.iter.rest(), ' ');
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return std.fmt.parseInt(usize, numSlice, 10) catch 0;
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}
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pub fn next(self: *dirIterator) ?cmdType {
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// Go through each command one by one
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while (self.iter.next()) |line| {
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// Not a valid input
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if (line.len <= 0) continue;
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// Changing folder (quitting or recursing)
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if (line.len > 5 and eql(line[0..5], "$ cd ")) {
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// Reached the end of the folder
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if (eql(line[5..], "..")) return cmdType.dirExit;
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// "cd" command not to parent, then it's a child
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return cmdType.dirEnter;
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}
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// Not a cd, maybe it's a size
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return cmdType.file;
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}
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// Exhausted the input
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return null;
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}
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pub fn reset(self: *dirIterator) *dirIterator {
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self.iter.reset();
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return self;
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}
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};
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