1 files changed, 44 insertions, 0 deletions
diff --git a/aoc/2021/10/part-two.zig b/aoc/2021/10/part-two.zig
new file mode 100644
index 0000000..4578272
--- /dev/null
+++ b/aoc/2021/10/part-two.zig
@@ -0,0 +1,44 @@
+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;
+const std = @import("std");
+const tokenize = std.mem.tokenize;
+
+pub fn main() !void {
+    var input = tokenize(@embedFile("input"), "\n");
+    var i: usize = 0;
+    var max_len: usize = 0;
+    while (input.next()) |line| : (i += 1) {
+        if (line.len > max_len)
+            max_len = line.len;
+    }
+    var stack = try Stack.alloc(page_allocator, max_len);
+    defer stack.free();
+
+    var scores = try page_allocator.alloc(usize, i);
+    defer page_allocator.free(scores);
+    input.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,
+            };
+        while (stack.pop()) |c| {
+            scores[i] *= 5;
+            scores[i] += @as(usize, switch (c) {
+                '(' => 1, '[' => 2, '{' => 3, '<' => 4,
+                else => unreachable,
+            });
+        }
+    }
+
+    sort(usize, scores, {}, desc);
+    i = indexOfScalar(usize, scores, 0).?;
+    print("{}\n", .{ scores[i / 2] });
+}