src/day09.zig

@@ -1,84 +0,0 @@
-const std = @import("std");
-const util = @import("util.zig");
-const mem = std.mem;
-
-pub fn main() !void {
-    const input = @embedFile("data/day09.txt");
-    const sln = try solve(util.gpa, input);
-    std.debug.print("{d}\n", .{sln.a});
-    std.debug.print("{d}\n", .{sln.b});
-}
-
-const Solution = struct {
-    a: isize,
-    b: isize,
-};
-
-fn drv(alloc: mem.Allocator, seq: []const isize) ![]const isize {
-    var list = try std.ArrayList(isize).initCapacity(alloc, seq.len - 1);
-    for (0..seq.len - 1) |i| {
-        try list.append(seq[i + 1] - seq[i]);
-    }
-    return list.toOwnedSlice();
-}
-
-fn zeroed(seq: []const isize) bool {
-    for (seq) |n| {
-        if (n != 0) return false;
-    }
-    return true;
-}
-
-fn solve(alloc: mem.Allocator, input: []const u8) !Solution {
-    var it = util.splitLines(input);
-    var prev_sum: isize = 0;
-    var next_sum: isize = 0;
-
-    while (it.next()) |line| {
-        if (line.len == 0) continue;
-        var seqs = std.ArrayList([]const isize).init(alloc);
-        defer seqs.deinit();
-        // Find zero derivation
-        try seqs.append(try util.parseIntsScalar(isize, alloc, line, .{}));
-        while (!zeroed(seqs.items[seqs.items.len - 1])) {
-            try seqs.append(try drv(alloc, seqs.items[seqs.items.len - 1]));
-        }
-        // Extrapolate
-        var next: isize = 0;
-        var prev: isize = 0;
-        for (seqs.items) |seq| {
-            next += seq[seq.len - 1];
-        }
-        for (0..seqs.items.len) |i| {
-            prev = seqs.items[seqs.items.len - i - 1][0] - prev;
-        }
-        for (seqs.items) |seq| {
-            // Clean up
-            alloc.free(seq);
-        }
-        prev_sum += prev;
-        next_sum += next;
-    }
-
-    return .{ .a = next_sum, .b = prev_sum };
-}
-
-test "silver" {
-    const input =
-        \\0 3 6 9 12 15
-        \\1 3 6 10 15 21
-        \\10 13 16 21 30 45
-    ;
-    const sln = try solve(std.testing.allocator, input);
-    try std.testing.expectEqual(@as(isize, 114), sln.a);
-}
-
-test "gold" {
-    const input =
-        \\0 3 6 9 12 15
-        \\1 3 6 10 15 21
-        \\10 13 16 21 30 45
-    ;
-    const sln = try solve(std.testing.allocator, input);
-    try std.testing.expectEqual(@as(isize, 2), sln.b);
-}