1 files changed, 48 insertions, 0 deletions
diff --git a/aoc/2021/04/part-one.zig b/aoc/2021/04/part-one.zig
new file mode 100644
index 0000000..67dc4e0
--- /dev/null
+++ b/aoc/2021/04/part-one.zig
@@ -0,0 +1,48 @@
+const parseUnsigned = std.fmt.parseUnsigned;
+const print = std.debug.print;
+const std = @import("std");
+const tokenize = std.mem.tokenize;
+
+pub fn main() !void {
+    var boards: [100][5]@Vector(5, u16) = undefined;
+    var input = tokenize(@embedFile("input"), "\n");
+    var order = tokenize(input.next().?, ",");
+    var i = @as(usize, 0);
+    while (i < 100) : (i += 1) {
+        var j = @as(usize, 0);
+        while (j < 5) : (j += 1) {
+            var row = tokenize(input.next().?, " ");
+            var k = @as(usize, 0);
+            while (k < 5) : (k += 1)
+                boards[i][j][k] = 1 + try parseUnsigned(u16, row.next().?, 10);
+        }
+    }
+
+    const result = loop: while (i > 0) : (i -= 1) {
+        const n = 1 + try parseUnsigned(u16, order.next().?, 10);
+        var j = @as(usize, 0);
+        while (j < 100) : (j += 1) {
+            var u = @as(usize, 0);
+            var k = @as(usize, 0);
+            while (k < 5) : (k += 1) {
+                var l = @as(usize, 0);
+                while (l < 5) : (l += 1) {
+                    if (boards[j][k][l] == n)
+                        boards[j][k][l] = 0
+                    else if (boards[j][k][l] > 0)
+                        u += 1;
+                }
+            }
+
+            const b = boards[j];
+            const sum = b[0] + b[1] + b[2] + b[3] + b[4];
+            const result = (@reduce(.Add, sum) - u) * (n - 1);
+            if (@reduce(.Min, sum) == 0)
+                break :loop result;
+            for (b) |v|
+                if (@reduce(.Max, v) == 0)
+                    break :loop result;
+        }
+    } else unreachable;
+    print("{}\n", .{ result });
+}