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const std = @import("std");
const example = @embedFile("example");
const input = @embedFile("input");
pub fn main() anyerror!void {
var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
defer arena.deinit();
const allocator = arena.allocator();
try std.testing.expectEqual(try solve(example, allocator), 24933642);
const result = try solve(input, allocator);
try std.io.getStdOut().writer().print("{}\n", .{result});
}
fn solve(puzzle: []const u8, allocator: std.mem.Allocator) !u64 {
var it = std.mem.tokenize(u8, puzzle, "\n");
var tot: usize = 0;
var n: usize = 0; // depth
var sizes = std.ArrayList(u64).init(allocator);
var stack = std.ArrayList(u64).init(allocator);
_ = it.next() orelse unreachable; // drop the cd /
try stack.append(0);
while (it.next()) |line| {
if (line[2] == 'c') { // a cd command
if (line[5] == '.') { // going up
const v = stack.pop();
n -= 1;
stack.items[n] += v;
try sizes.append(v);
} else { // going down
n += 1;
try stack.append(0);
}
} else if (line[2] == 'l') { // a ls command
continue;
} else if (line[2] == 'r') { // a dir entry in a ls command
continue;
} else { // a file entry in a ls command
var elts = std.mem.split(u8, line, " ");
const v = try std.fmt.parseInt(u64, elts.next() orelse unreachable, 10);
stack.items[n] += v;
tot += v;
}
}
while (n > 1) : (n -= 1) { // we unwrap the cd up to /
const v = stack.pop();
n -= 1;
stack.items[n] += v;
try sizes.append(v);
}
try sizes.append(stack.items[n]); // we do not forget the last one
n = 30000000 - (70000000 - tot); // the amount of space we need to free
// let's find the minimum that is the closest to that
tot = 70000000;
for (sizes.items) |v| {
if (v > n and v < tot) {
tot = v;
}
}
return tot;
}
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