From dbb917c8ef7095c61e1c641404e9d0ecca3ef766 Mon Sep 17 00:00:00 2001
From: Patrick Auernig <patrick.auernig@mykolab.com>
Date: Sun, 10 Dec 2023 21:12:28 +0100
Subject: [PATCH] Add solution for 2023 day 06 part 2

---
 2023/README.md           |  2 +-
 2023/day-06/common.zig   | 30 ++++++++++++++++++++++++++++++
 2023/day-06/part_one.zig | 30 ++----------------------------
 2023/day-06/part_two.zig | 34 ++++++++++++++++++++++++++++++++++
 README.md                |  2 +-
 5 files changed, 68 insertions(+), 30 deletions(-)
 create mode 100644 2023/day-06/part_two.zig

diff --git a/2023/README.md b/2023/README.md
index 32dee94..0d0d134 100644
--- a/2023/README.md
+++ b/2023/README.md
@@ -9,7 +9,7 @@
 | [03] |   ✓    |   ✓    | [Zig]    |
 | [04] |   ✓    |   ✓    | [Zig]    |
 | [05] |   ✓    |   ✓    | [Zig]    |
-| [06] |        |        |          |
+| [06] |   ✓    |   ✓    | [Zig]    |
 | [07] |        |        |          |
 | [08] |        |        |          |
 | [09] |        |        |          |
diff --git a/2023/day-06/common.zig b/2023/day-06/common.zig
index ec11ae3..21ff08f 100644
--- a/2023/day-06/common.zig
+++ b/2023/day-06/common.zig
@@ -13,6 +13,36 @@ pub const Races = struct {
 
 const List = std.ArrayList;
 
+pub fn calculate(time: u64, record_dist: u64) u64 {
+    var min: u64 = undefined;
+
+    for (1..time) |speed| {
+        const rem_race_time = time - speed;
+        const dist = rem_race_time * speed;
+        if (dist > record_dist) {
+            min = @intCast(speed);
+            break;
+        }
+    }
+
+    var max: u64 = undefined;
+
+    var speed: u64 = time - 1;
+    while (speed > 0) {
+        const rem_race_time = time - speed;
+        const dist = rem_race_time * speed;
+
+        if (dist > record_dist) {
+            max = speed;
+            break;
+        }
+
+        speed -= 1;
+    }
+
+    return max - min + 1;
+}
+
 pub fn parse(data: []const u8) !Races {
     var lines = std.mem.tokenizeScalar(u8, data, '\n');
 
diff --git a/2023/day-06/part_one.zig b/2023/day-06/part_one.zig
index 13f6fe8..86a50a0 100644
--- a/2023/day-06/part_one.zig
+++ b/2023/day-06/part_one.zig
@@ -9,38 +9,12 @@ pub fn main() !void {
     const races = try common.parse(data);
     defer races.deinit();
 
-    var prod: u32 = 1;
+    var prod: u64 = 1;
 
     for (races.times.items, 0..) |race_time, i| {
         const race_record = races.distances.items[i];
 
-        var min: u32 = undefined;
-
-        for (1..race_time) |speed| {
-            const rem_race_time = race_time - speed;
-            const dist = rem_race_time * speed;
-            if (dist > race_record) {
-                min = @intCast(speed);
-                break;
-            }
-        }
-
-        var max: u32 = undefined;
-
-        var speed: u32 = race_time - 1;
-        while (speed > 0) {
-            const rem_race_time = race_time - speed;
-            const dist = rem_race_time * speed;
-
-            if (dist > race_record) {
-                max = speed;
-                break;
-            }
-
-            speed -= 1;
-        }
-
-        const nums_beat = max - min + 1;
+        const nums_beat = common.calculate(race_time, race_record);
 
         prod *= nums_beat;
     }
diff --git a/2023/day-06/part_two.zig b/2023/day-06/part_two.zig
new file mode 100644
index 0000000..3318cf5
--- /dev/null
+++ b/2023/day-06/part_two.zig
@@ -0,0 +1,34 @@
+const std = @import("std");
+const common = @import("common.zig");
+const alloc = std.heap.page_allocator;
+const Buffer = std.ArrayList(u8);
+
+const data = @embedFile("inputs/puzzle.txt");
+
+pub fn main() !void {
+    const stdout = std.io.getStdOut().writer();
+
+    const races = try common.parse(data);
+    defer races.deinit();
+
+    const time = try concat_numbers(races.times.items);
+    const record = try concat_numbers(races.distances.items);
+
+    const nums_beat = common.calculate(time, record);
+
+    try stdout.print("{d}\n", .{nums_beat});
+}
+
+fn concat_numbers(nums: []const u32) !u64 {
+    var buf = Buffer.init(alloc);
+    defer buf.deinit();
+
+    for (nums) |race_times| {
+        const segment = try std.fmt.allocPrint(alloc, "{d}", .{race_times});
+        try buf.appendSlice(segment);
+    }
+
+    const num = try std.fmt.parseInt(u64, buf.items, 10);
+
+    return num;
+}
diff --git a/README.md b/README.md
index af438d7..f044722 100644
--- a/README.md
+++ b/README.md
@@ -10,4 +10,4 @@
 -   [2020](2020/README.md) (20% completed)
 -   [2021](2021/README.md) (68% completed)
 -   [2022](2022/README.md) (54% completed)
--   [2023](2023/README.md) (20% completed)
+-   [2023](2023/README.md) (24% completed)