day08 part1
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src/day08.zig
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75
src/day08.zig
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const std = @import("std");
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const util = @import("util.zig");
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const mem = std.mem;
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pub fn main() !void {
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const input = @embedFile("data/day08.txt");
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const sln = try solve(util.gpa, input);
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std.debug.print("{d}\n", .{sln.a});
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std.debug.print("{d}\n", .{sln.b});
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}
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const Solution = struct {
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a: usize,
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b: usize,
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};
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const Step = struct {
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left: [3]u8,
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right: [3]u8,
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};
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fn solve(alloc: mem.Allocator, input: []const u8) !Solution {
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var states = std.AutoHashMap([3]u8, Step).init(alloc);
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defer states.deinit();
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var position: [3]u8 = "AAA".*;
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var it = util.splitLines(input);
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const steps = it.next().?;
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while (it.next()) |line| {
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if (line.len == 0) continue;
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try states.put(line[0..3].*, .{ .left = line[7..10].*, .right = line[12..15].* });
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}
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var count: u16 = 0;
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while (!mem.eql(u8, &position, "ZZZ")) : (count += 1) {
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const currState = states.get(position) orelse break; // ???????
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position = if (steps[count % steps.len] == 'L') currState.left else currState.right;
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}
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return .{ .a = count, .b = 0 };
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}
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test "silver" {
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const input =
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\\RL
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\\
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\\AAA = (BBB, CCC)
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\\BBB = (DDD, EEE)
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\\CCC = (ZZZ, GGG)
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\\DDD = (DDD, DDD)
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\\EEE = (EEE, EEE)
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\\GGG = (GGG, GGG)
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\\ZZZ = (ZZZ, ZZZ)
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;
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const sln = try solve(std.testing.allocator, input);
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try std.testing.expectEqual(@as(usize, 2), sln.a);
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}
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test "gold" {
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const input =
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\\LR
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\\
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\\11A = (11B, XXX)
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\\11B = (XXX, 11Z)
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\\11Z = (11B, XXX)
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\\22A = (22B, XXX)
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\\22B = (22C, 22C)
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\\22C = (22Z, 22Z)
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\\22Z = (22B, 22B)
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\\XXX = (XXX, XXX)
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;
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const sln = try solve(std.testing.allocator, input);
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try std.testing.expectEqual(@as(usize, 0), sln.b);
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}
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