2024 Day 22 Part 1

2024/src/day22.zig

@@ -0,0 +1,50 @@
+const std = @import("std");
+const aoc = @import("aoc.zig");
+
+const Allocator = std.mem.Allocator;
+const List = std.ArrayList;
+const Map = std.AutoHashMap;
+const Set = aoc.AutoHashSet;
+const PriorityQueue = std.PriorityQueue;
+
+pub fn main() !void {
+    var gpa: std.heap.GeneralPurposeAllocator(.{}) = .{};
+    defer _ = gpa.deinit();
+    const allocator = gpa.allocator();
+
+    const text = try aoc.readAll(allocator, "input/day22.txt");
+    defer allocator.free(text);
+
+    var lines = std.mem.tokenizeScalar(u8, text, '\n');
+
+    var seeds = List(u64).init(allocator);
+    defer seeds.deinit();
+    while (lines.next()) |line| {
+        const seed = try std.fmt.parseInt(u64, line, 10);
+        try seeds.append(seed);
+    }
+
+    var bw = std.io.bufferedWriter(std.io.getStdOut().writer());
+    const stdout = bw.writer();
+
+    try stdout.print("{}\n", .{part1(seeds.items)});
+    try bw.flush();
+}
+
+fn part1(seeds: []u64) u64 {
+    var sum: u64 = 0;
+    for (seeds) |seed| {
+        sum += simulate(seed, 2000);
+    }
+    return sum;
+}
+
+fn simulate(seed: u64, steps: usize) u64 {
+    var n: u64 = seed;
+    for (0..steps) |_| {
+        n = ((n * 64) ^ n) % 16777216;
+        n = ((n / 32) ^ n) % 16777216;
+        n = ((n * 2048) ^ n) % 16777216;
+    }
+    return n;
+}