unwash day06 or something

src/day06.zig

@@ -0,0 +1,78 @@
+const std = @import("std");
+const util = @import("util.zig");
+const mem = std.mem;
+
+pub fn main() !void {
+    const input = @embedFile("data/day06.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: usize,
+    b: usize,
+};
+
+const Race = struct {
+    time: usize,
+    distance: usize,
+};
+
+fn solve(alloc: mem.Allocator, input: []const u8) !Solution {
+    var result: usize = 1;
+    {
+        var it = util.splitLines(input);
+        const times = try util.parseIntsScalar(usize, alloc, it.next().?[10..], .{});
+        const distances = try util.parseIntsScalar(usize, alloc, it.next().?[10..], .{});
+        defer alloc.free(times);
+        defer alloc.free(distances);
+
+        for (times, distances) |time, minDistance| {
+            var winning: usize = 0;
+            for (0..time - 1) |speed| {
+                const distance = speed * (time - speed);
+                if (distance > minDistance) winning += 1;
+            }
+            result *= winning;
+        }
+    }
+
+    var result2: usize = 1;
+    {
+        var it = util.splitLines(input);
+        var td: [2]usize = undefined;
+        for (0..td.len) |i| {
+            const line = try mem.replaceOwned(u8, alloc, it.next().?[10..], " ", "");
+            defer alloc.free(line);
+            td[i] = try std.fmt.parseInt(usize, line, 10);
+        }
+
+        var winning2: usize = 0;
+        for (0..td[0] - 1) |speed| {
+            const distance = speed * (td[0] - speed);
+            if (distance > td[1]) winning2 += 1;
+        }
+        result2 *= winning2;
+    }
+
+    return .{ .a = result, .b = result2 };
+}
+
+test "silver" {
+    const input =
+        \\Time:      7  15   30
+        \\Distance:  9  40  200
+    ;
+    const sln = try solve(std.testing.allocator, input);
+    try std.testing.expectEqual(@as(usize, 288), sln.a);
+}
+
+test "gold" {
+    const input =
+        \\Time:      7  15   30
+        \\Distance:  9  40  200
+    ;
+    const sln = try solve(std.testing.allocator, input);
+    try std.testing.expectEqual(@as(usize, 71503), sln.b);
+}