4 files changed, 56 insertions, 74 deletions
diff --git a/aoc/2021/10/Stack.zig b/aoc/2021/10/Stack.zig
new file mode 100644
index 0000000..1aab8eb
--- /dev/null
+++ b/aoc/2021/10/Stack.zig
@@ -0,0 +1,35 @@
+const Allocator = @import("std").mem.Allocator;
+const Self = @This();
+
+allocator: *Allocator,
+memory: []u8,
+len: usize,
+
+pub fn alloc(allocator: *Allocator, size: usize) !Self {
+    return Self{
+        .allocator = allocator,
+        .memory = try allocator.alloc(u8, size),
+        .len = 0,
+    };
+}
+
+pub fn free(self: *Self) void {
+    self.allocator.free(self.memory);
+    self.* = undefined;
+}
+
+pub fn push(self: *Self, node: u8) void {
+    self.memory[self.len] = node;
+    self.len += 1;
+}
+
+pub fn pop(self: *Self) ?u8 {
+    if (self.len < 1)
+        return null;
+    self.len -= 1;
+    return self.memory[self.len];
+}
+
+pub fn reset(self: *Self) void {
+    self.len = 0;
+}
diff --git a/aoc/2021/10/part-one.zig b/aoc/2021/10/part-one.zig
index 27ac20c..130fc4a 100644
--- a/aoc/2021/10/part-one.zig
+++ b/aoc/2021/10/part-one.zig
@@ -1,4 +1,4 @@
-const Stack = @import("stack.zig").Stack;
+const Stack = @import("Stack.zig");
 const page_allocator = std.heap.page_allocator;
 const print = std.debug.print;
 const std = @import("std");
@@ -11,17 +11,17 @@ pub fn main() !void {
         if (line.len > max_len)
             max_len = line.len;
     }
-    var stack = try Stack(u8).alloc(page_allocator, max_len);
+    var stack = try Stack.alloc(page_allocator, max_len);
     defer stack.free();
 
     var sum: usize = 0;
     defer print("{}\n", .{ sum });
     input.reset();
-    while (input.next()) |line| {
+    while (input.next()) |line| : (stack.reset())
         for (line) |c|
             switch (c) {
                 '(', '[', '{', '<' => stack.push(c),
-                else => if (stack.pop() ^ c > 6) {
+                else => if (stack.pop().? ^ c > 6) {
                     sum += @as(usize, switch (c) {
                         ')' => 3, ']' => 57, '}' => 1197, '>' => 25137,
                         else => unreachable,
@@ -29,6 +29,4 @@ pub fn main() !void {
                     break;
                 },
             };
-        stack.reset();
-    }
 }
diff --git a/aoc/2021/10/part-two.zig b/aoc/2021/10/part-two.zig
index 6e5b11d..4578272 100644
--- a/aoc/2021/10/part-two.zig
+++ b/aoc/2021/10/part-two.zig
@@ -1,5 +1,6 @@
-const Stack = @import("stack.zig").Stack;
-const asc = std.sort.asc(usize);
+const Stack = @import("Stack.zig");
+const desc = std.sort.desc(usize);
+const indexOfScalar = std.mem.indexOfScalar;
 const page_allocator = std.heap.page_allocator;
 const print = std.debug.print;
 const sort = std.sort.sort;
@@ -8,49 +9,36 @@ const tokenize = std.mem.tokenize;
 
 pub fn main() !void {
     var input = tokenize(@embedFile("input"), "\n");
-    var incomplete: usize = 0;
+    var i: usize = 0;
     var max_len: usize = 0;
-    while (input.next()) |line| : (incomplete += 1) {
+    while (input.next()) |line| : (i += 1) {
         if (line.len > max_len)
             max_len = line.len;
     }
-
-    var stack = try Stack(u8).alloc(page_allocator, max_len);
+    var stack = try Stack.alloc(page_allocator, max_len);
     defer stack.free();
-    input.reset();
-    while (input.next()) |line| {
-        for (line) |c|
-            switch (c) {
-                '(', '[', '{', '<' => stack.push(c),
-                else => if (stack.pop() ^ c > 6) {
-                    incomplete -= 1;
-                    break;
-                },
-            };
-        stack.reset();
-    }
 
-    var scores = try page_allocator.alloc(usize, incomplete);
+    var scores = try page_allocator.alloc(usize, i);
     defer page_allocator.free(scores);
     input.reset();
-    loop: while (input.next()) |line| {
-        stack.reset();
+    loop: while (input.next()) |line| : (stack.reset()) {
+        i -= 1;
+        scores[i] = 0;
         for (line) |c|
             switch (c) {
                 '(', '[', '{', '<' => stack.push(c),
-                else => if (stack.pop() ^ c > 6) continue :loop,
+                else => if (stack.pop().? ^ c > 6) continue :loop,
             };
-        incomplete -= 1;
-        scores[incomplete] = 0;
-        while (stack.len > 0) {
-            scores[incomplete] *= 5;
-            scores[incomplete] += @as(usize, switch (stack.pop()) {
+        while (stack.pop()) |c| {
+            scores[i] *= 5;
+            scores[i] += @as(usize, switch (c) {
                 '(' => 1, '[' => 2, '{' => 3, '<' => 4,
                 else => unreachable,
             });
         }
     }
 
-    sort(usize, scores, {}, asc);
-    print("{}\n", .{ scores[scores.len / 2] });
+    sort(usize, scores, {}, desc);
+    i = indexOfScalar(usize, scores, 0).?;
+    print("{}\n", .{ scores[i / 2] });
 }
diff --git a/aoc/2021/10/stack.zig b/aoc/2021/10/stack.zig
deleted file mode 100644
index 1002d61..0000000
--- a/aoc/2021/10/stack.zig
+++ /dev/null
@@ -1,39 +0,0 @@
-const Allocator = @import("std").mem.Allocator;
-
-pub fn Stack(comptime T: type) type {
-    return struct {
-        allocator: *Allocator,
-        memory: []T,
-        len: usize,
-
-        const Self = @This();
-
-        pub fn alloc(allocator: *Allocator, size: usize) !Self {
-            return Self{
-                .allocator = allocator,
-                .memory = try allocator.alloc(T, size),
-                .len = 0,
-            };
-        }
-
-        pub fn free(self: *Self) void {
-            self.allocator.free(self.memory);
-            self.* = undefined;
-        }
-
-        pub fn push(self: *Self, node: T) void {
-            self.memory[self.len] = node;
-            self.len += 1;
-        }
-
-        pub fn pop(self: *Self) T {
-            self.len -= 1;
-            return self.memory[self.len];
-        }
-
-        pub fn reset(self: *Self) void {
-            self.len = 0;
-        }
-    };
-}
-