advent-of-code/2024/day2.zig

const std = @import("std");
const print = std.debug.print;

const util = @import("util.zig");

fn isSafe(items: []const i16) bool {
    if (!std.sort.isSorted(i16, items, {}, std.sort.asc(i16)) and
        !std.sort.isSorted(i16, items, {}, std.sort.desc(i16))) return false;

    for (1..items.len) |i| {
        if (@abs(items[i] - items[i - 1]) > 3 or items[i] == items[i - 1]) return false;
    }
    return true;
}

pub fn main() !void {
    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
    const allocator = gpa.allocator();

    const input = try util.readAllInput(2, allocator);

    var safe: u16 = 0;
    var safe_with_dampener: u16 = 0;
    var lines = std.mem.tokenizeScalar(u8, input, '\n');
    outer: while (lines.next()) |line| {
        const levels = try util.inputToArrayList(i16, allocator, line);
        defer levels.deinit();

        // PART 1
        if (isSafe(levels.items)) {
            safe += 1;
            continue;
        }
        // PART 2
        for (0..levels.items.len) |i| {
            var damp_levels = try levels.clone();
            defer damp_levels.deinit();
            _ = damp_levels.orderedRemove(i);
            if (isSafe(damp_levels.items)) {
                safe_with_dampener += 1;
                continue :outer;
            }
        }
    }

    print("PART 1 - SAFE REPORTS:       {d}\n", .{safe});
    print("PART 2 - SAFE WITH DAMPENER: {d}\n", .{safe + safe_with_dampener});
}