day12 part2

jesus

src/day12.zig

@@ -14,8 +14,8 @@ const Solution = struct {
     b: usize,
 };
 
-fn hash(alloc: mem.Allocator, pattern: []const u8, groups: []const u8, curr_group: u8) ![]const u8 {
-    var a = try std.ArrayList(u8).initCapacity(alloc, pattern.len + groups.len + curr_group);
+fn hash(alloc: mem.Allocator, pattern: []const u8, groups: []const u8, curr_group: u8) ![]u8 {
+    var a = try std.ArrayList(u8).initCapacity(alloc, pattern.len + groups.len + 1);
     try a.appendSlice(pattern);
     try a.appendSlice(groups);
     try a.append(curr_group);
@@ -25,10 +25,10 @@ fn hash(alloc: mem.Allocator, pattern: []const u8, groups: []const u8, curr_grou
 // Mystery records to whether they fit.
 var memo: std.StringHashMap(u32) = undefined;
 
-fn copy(comptime T: type, alloc: mem.Allocator, s: []const T) ![]T {
-    var a = try std.ArrayList(T).initCapacity(alloc, s.len);
-    try a.insertSlice(0, s);
-    return try a.toOwnedSlice();
+fn clone(comptime T: type, alloc: mem.Allocator, s: []const T) ![]T {
+    var a = try alloc.alloc(T, s.len);
+    @memcpy(a, s);
+    return a;
 }
 
 fn solvePattern(alloc: mem.Allocator, pattern: []const u8, groups: []const u8, curr_group: u8) !u32 {
@@ -37,12 +37,12 @@ fn solvePattern(alloc: mem.Allocator, pattern: []const u8, groups: []const u8, c
     const h = try hash(alloc, pattern, groups, curr_group);
     if (memo.get(h)) |m| {
         alloc.free(h);
-        std.debug.print("==> short-circuit {}\n", .{m});
+        std.debug.print("== short-circuit {}\n", .{m});
         return m;
     }
 
     if (pattern.len == 0) {
-        std.debug.print("=> done ok: {}\n", .{groups.len == 0});
+        std.debug.print("== done {}\n", .{groups.len == 0});
         return if (groups.len == 0) 1 else 0;
     }
 
@@ -56,6 +56,7 @@ fn solvePattern(alloc: mem.Allocator, pattern: []const u8, groups: []const u8, c
                 }
                 // Special-case last #
                 if (pattern.len == 1 and groups.len == 1 and groups[0] == curr_group + 1) {
+                    std.debug.print("== done true\n", .{});
                     break :b 1;
                 }
                 break :b try solvePattern(alloc, pattern[1..], groups, curr_group + 1);
@@ -68,7 +69,6 @@ fn solvePattern(alloc: mem.Allocator, pattern: []const u8, groups: []const u8, c
                         break :b 0;
                     } else {
                         // Group done
-                        std.debug.print("=> group {} ok\n", .{groups[0]});
                         break :b try solvePattern(alloc, pattern[1..], groups[1..], 0);
                     }
                 } else {
@@ -77,9 +77,9 @@ fn solvePattern(alloc: mem.Allocator, pattern: []const u8, groups: []const u8, c
                 }
             },
             '?' => {
-                const p1 = try copy(u8, alloc, pattern);
+                const p1 = try clone(u8, alloc, pattern);
                 defer alloc.free(p1);
-                const p2 = try copy(u8, alloc, pattern);
+                const p2 = try clone(u8, alloc, pattern);
                 defer alloc.free(p2);
 
                 p1[0] = '#';
@@ -99,12 +99,24 @@ fn solvePattern(alloc: mem.Allocator, pattern: []const u8, groups: []const u8, c
     return res;
 }
 
+fn unfold(alloc: mem.Allocator, input: []const u8, sep: u8) ![]const u8 {
+    var buf = try std.ArrayList(u8).initCapacity(alloc, input.len * 5 + 5);
+    for (0..5) |i| {
+        if (i > 0 and sep > 0) try buf.append(sep);
+        try buf.appendSlice(input);
+    }
+    return try buf.toOwnedSlice();
+}
+
 fn solve(alloc: mem.Allocator, input: []const u8) !Solution {
     memo = std.StringHashMap(u32).init(alloc);
     defer memo.deinit();
 
-    var sum: u32 = 0;
+    var sum1: u32 = 0;
+    var sum2: u32 = 0;
+
     var it = util.splitLines(input);
+    var i: u32 = 0;
     while (it.next()) |line| {
         if (line.len == 0) continue;
 
@@ -114,9 +126,16 @@ fn solve(alloc: mem.Allocator, input: []const u8) !Solution {
         const groups = try util.parseIntsScalar(u8, alloc, raw_groups, .{ .sep = ',' });
         defer alloc.free(groups);
 
-        std.debug.print("-----------------------------------------------\n", .{});
-        sum += try solvePattern(alloc, pattern, groups, 0);
-        std.debug.print("{}\n", .{sum});
+        const unfolded_pattern = try unfold(alloc, pattern, '?');
+        const unfolded_groups = try unfold(alloc, groups, 0);
+        defer alloc.free(unfolded_pattern);
+        defer alloc.free(unfolded_groups);
+
+        std.debug.print("---- {} ----\n", .{i});
+        sum1 += try solvePattern(alloc, pattern, groups, 0);
+        sum2 += try solvePattern(alloc, unfolded_pattern, unfolded_groups, 0);
+        std.debug.print("{} {}\n", .{ sum1, sum2 });
+        i += 1;
     }
 
     var mkeys = memo.keyIterator();
@@ -124,7 +143,7 @@ fn solve(alloc: mem.Allocator, input: []const u8) !Solution {
         alloc.free(k.*);
     }
 
-    return .{ .a = sum, .b = 0 };
+    return .{ .a = sum1, .b = sum2 };
 }
 
 test "silver" {
@@ -140,15 +159,34 @@ test "silver" {
     try std.testing.expectEqual(@as(usize, 21), sln.a);
 }
 
-test "gold" {
+test "gold-2" {
     const input =
-        \\???.### 1,1,3
         \\.??..??...?##. 1,1,3
-        \\?#?#?#?#?#?#?#? 1,3,1,6
+    ;
+    const sln = try solve(std.testing.allocator, input);
+    try std.testing.expectEqual(@as(usize, 16384), sln.b);
+}
+
+test "gold-4" {
+    const input =
         \\????.#...#... 4,1,1
+    ;
+    const sln = try solve(std.testing.allocator, input);
+    try std.testing.expectEqual(@as(usize, 16), sln.b);
+}
+
+test "gold-5" {
+    const input =
         \\????.######..#####. 1,6,5
+    ;
+    const sln = try solve(std.testing.allocator, input);
+    try std.testing.expectEqual(@as(usize, 2500), sln.b);
+}
+
+test "gold-6" {
+    const input =
         \\?###???????? 3,2,1
     ;
     const sln = try solve(std.testing.allocator, input);
-    try std.testing.expectEqual(@as(usize, 525152), sln.b);
+    try std.testing.expectEqual(@as(usize, 506250), sln.b);
 }