1 files changed, 7 insertions(+), 29 deletions(-)

M 5/main.zig

@@ 5,39 5,20 @@ const fmt = std.fmt;
 
 const print = std.debug.print;
 
-fn array_list(a: *mem.Allocator) !std.ArrayList([]const u8) {
+fn run(a: *mem.Allocator) [2]usize {
     var strings = mem.split(input, "\n");
-    var list = std.ArrayList([]const u8).init(a);
-    while (strings.next()) |string| {
-        try list.append(string);
-    }
-    return list;
-}
-
-fn divCeil(x: usize, y: usize) usize {
-    return (x/y) + @boolToInt(x%y != 0);
-}
-
-pub fn parts(slice: [][]const u8, a: *mem.Allocator) [2]usize {
     var ids = std.AutoHashMap(usize, bool).init(a);
     var max: usize = 0;
-    for (slice) |item| {
-        var row: [2]usize = .{0, 127};
-        var column: [2]usize = .{0, 7};
+    while (strings.next()) |item| {
+        var id: usize = 0;
         for (item) |c| {
-            switch (c) {
-                'F' => row[1] = @divFloor(row[1] + row[0], 2),
-                'B' => row[0] = divCeil(row[1] + row[0], 2),
-                'L' => column[1] = @divFloor(column[1] + column[0], 2),
-                'R' => column[0] = divCeil(column[1] + column[0], 2),
-                else => unreachable
-            }
+            id <<= 1;
+            id += @boolToInt(c == 'B' or c == 'R');
         }
-        var id = row[0] * 8 + column[1];
         ids.put(id, true) catch unreachable;
         if (id > max) max = id;
     }
-    var i: usize = max;
+    var i = max;
     while (i > 0) : ( i -= 1 ) {
         _ = ids.get(i) orelse return .{max, i};
     }


@@ 47,9 28,6 @@ pub fn parts(slice: [][]const u8, a: *mem.Allocator) [2]usize {
 pub fn main() !void {
     var gpa = std.heap.GeneralPurposeAllocator(.{}){};
     const a = &gpa.allocator;
-    var list = try array_list(a);
-    const slice = list.items;
-
-    var p = parts(slice, a);
+    var p = run(a);
     print("part 1: {}\npart 2: {}\n", .{p[0], p[1]});
 }=
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