remove naive intersection impl

1 files changed, 20 insertions, 29 deletions

diff --git a/day-3/main.zig b/day-3/main.zig
index 0bba2f3..57057bf 100644
--- a/day-3/main.zig
+++ b/day-3/main.zig
@@ -1,48 +1,39 @@
 const std = @import("std");
-const dupl_values = @import("util/mem.zig").dupl_values;
 
-pub fn puzzle_1(allocator: std.mem.Allocator, input: []u8) !u16 {
+pub fn puzzle_1(input: []const u8) u16 {
     var iter = std.mem.split(u8, input, "\n");
 
     var count: u16 = 0;
     while (iter.next()) |line| {
-        const duplicates = try dupl_values(
-            u8,
-            allocator,
-            &[_][]const u8{
-                line[0 .. line.len / 2],
-                line[line.len / 2 ..],
-            },
-        );
-        defer allocator.free(duplicates);
-
-        for (duplicates) |char| {
-            count += char_to_priority(char);
+        var p1: u64 = 0;
+        var p2: u64 = 0;
+
+        for (line[0 .. line.len / 2]) |_, i| {
+            p1 |= @as(u64, 1) << @intCast(u6, line[i] - 65); // 65 == 'A'
+            p2 |= @as(u64, 1) << @intCast(u6, line[i + line.len / 2] - 65);
         }
+
+        count += char_to_priority(@intCast(u8, 65 + 63) - @clz(p1 & p2));
     }
 
     return count;
 }
 
-pub fn puzzle_2(allocator: std.mem.Allocator, input: []u8) !u16 {
+pub fn puzzle_2(input: []const u8) u16 {
     var iter = std.mem.split(u8, input, "\n");
 
     var count: u16 = 0;
-    while (iter.next()) |line| {
-        const duplicates = try dupl_values(
-            u8,
-            allocator,
-            &[_][]const u8{
-                line,
-                iter.next().?,
-                iter.next().?,
-            },
-        );
-        defer allocator.free(duplicates);
-
-        for (duplicates) |char| {
-            count += char_to_priority(char);
+    mainLoop: while (true) {
+        var parts = std.mem.zeroes([3]u64);
+
+        for (parts) |*p| {
+            const line = iter.next() orelse break :mainLoop;
+            for (line) |_, i| {
+                p.* |= @as(u64, 1) << @intCast(u6, line[i] - 65);
+            }
         }
+
+        count += char_to_priority(@intCast(u8, 65 + 63) - @clz(parts[0] & parts[1] & parts[2]));
     }
 
     return count;