[Day 22] Add solution

Author: goggle

README.md

@@ -30,8 +30,8 @@ This Julia package contains my solutions for [Advent of Code 2024](https://adven
 | 18 | [:white_check_mark:](https://adventofcode.com/2024/day/18) |2.964 ms | 5.64 MiB | [:white_check_mark:](https://github.com/goggle/AdventOfCode2024.jl/blob/main/src/day18.jl) |
 | 19 | [:white_check_mark:](https://adventofcode.com/2024/day/19) | 59.678 ms | 3.41 MiB| [:white_check_mark:](https://github.com/goggle/AdventOfCode2024.jl/blob/main/src/day19.jl) |
 | 20 | [:white_check_mark:](https://adventofcode.com/2024/day/20) | 227.453 ms | 224.97 MiB| [:white_check_mark:](https://github.com/goggle/AdventOfCode2024.jl/blob/main/src/day20.jl) |
+| 22 | [:white_check_mark:](https://adventofcode.com/2024/day/22) | 241.724 ms | 78.80 MiB | [:white_check_mark:](https://github.com/goggle/AdventOfCode2024.jl/blob/main/src/day22.jl) |
 <!-- | 21 | [:white_check_mark:](https://adventofcode.com/2024/day/21) | 9.675 ms | 7.19 MiB | [:white_check_mark:](https://github.com/goggle/AdventOfCode2024.jl/blob/main/src/day21.jl) | -->
-<!-- | 22 | [:white_check_mark:](https://adventofcode.com/2024/day/22) | 790.712 ms | 631.26 MiB | [:white_check_mark:](https://github.com/goggle/AdventOfCode2024.jl/blob/main/src/day22.jl) | -->
 <!-- | 23 | [:white_check_mark:](https://adventofcode.com/2024/day/23) | 2.979 s | 9.69 MiB | [:white_check_mark:](https://github.com/goggle/AdventOfCode2024.jl/blob/main/src/day23.jl) | -->
 <!-- | 24 | [:white_check_mark:](https://adventofcode.com/2024/day/24) | 43.214 ms | 49.77 MiB | [:white_check_mark:](https://github.com/goggle/AdventOfCode2024.jl/blob/main/src/day24.jl) | -->
 <!-- | 25 | [:white_check_mark:](https://adventofcode.com/2024/day/25) | 69.476 ms | 62.03 MiB | [:white_check_mark:](https://github.com/goggle/AdventOfCode2024.jl/blob/main/src/day25.jl) | -->

data

@@ -3,7 +3,7 @@ module AdventOfCode2024
 using BenchmarkTools
 using Printf
 
-solvedDays = 1:21
+solvedDays = 1:22
 # Include the source files:
 for day in solvedDays
     ds = @sprintf("%02d", day)

src/AdventOfCode2024.jl

@@ -0,0 +1,59 @@
+module Day22
+
+using AdventOfCode2024
+using DataStructures
+
+function day22(input::String = readInput(joinpath(@__DIR__, "..", "data", "day22.txt")))
+    secrets = parse.(Int, split(rstrip(input), '\n'))
+    p1 = 0
+
+    nbananas = Dict{Int,Int}()
+    for i1 ∈ 0:18
+        for i2 ∈ 0:18
+            for i3 ∈ 0:18
+                for i4 ∈ 0:18
+                    nbananas[(i1<<15, i2<<10, i3<<5, i4) |> sum] = 0
+                end
+            end
+        end
+    end
+
+    for secret ∈ secrets
+        seen = Set{Int}()
+        cb = CircularBuffer{Int8}(4)
+        nsecret = secret
+        price = nsecret % 10
+        for _ ∈ 1:3
+            nsecret = next_secret_number(nsecret)
+            nprice = nsecret % 10
+            push!(cb, nprice - price)
+            price = nprice
+        end
+        for _ ∈ 4:2000
+            nsecret = next_secret_number(nsecret)
+            nprice = nsecret % 10
+            push!(cb, nprice - price)
+            price = nprice
+
+            diffseq = ((cb[1] + 9) << 15, (cb[2] + 9) << 10, (cb[3] + 9) << 5, cb[4] + 9) |> sum
+            if diffseq ∉ seen
+                push!(seen, diffseq)
+                nbananas[diffseq] += price
+            end
+        end
+        p1 += nsecret
+    end
+
+    return [p1, maximum(values(nbananas))]
+end
+
+function next_secret_number(secret::Int)
+    step1 = mix(secret << 6, secret) |> prune
+    step2 = mix(step1 >> 5, step1) |> prune
+    return mix(step2 << 11, step2) |> prune
+end
+
+mix(number::Int, secret::Int) = xor(number, secret)
+prune(secret::Int) = secret % 16777216
+
+end # module

src/day22.jl

@@ -326,4 +326,20 @@ end
 
 @testset "Day 20" begin
     @testset AdventOfCode2024.Day20.day20() == [1411, 1010263]
+end
+
+@testset "Day 22" begin
+    sample = "1\n" *
+             "10\n" *
+             "100\n" *
+             "2024\n"
+    @test AdventOfCode2024.Day22.day22(sample) == [37327623, 24]
+
+    sample2 = "1\n" *
+              "2\n" *
+              "3\n" *
+              "2024\n"
+    @test AdventOfCode2024.Day22.day22(sample2) == [37990510, 23]
+
+    @test AdventOfCode2024.Day22.day22() == [13185239446, 1501]
 end