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| 1 | +const std = @import("std"); |
| 2 | + |
| 3 | +pub fn main() !void { |
| 4 | + var file = try std.fs.cwd().openFile("input", .{}); |
| 5 | + defer file.close(); |
| 6 | + |
| 7 | + var buf_reader = std.io.bufferedReader(file.reader()); |
| 8 | + var in_stream = buf_reader.reader(); |
| 9 | + |
| 10 | + var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator); |
| 11 | + defer arena.deinit(); |
| 12 | + |
| 13 | + const allocator = &arena.allocator; |
| 14 | + |
| 15 | + var map_list = std.ArrayList(u8).init(allocator); |
| 16 | + map_list.deinit(); |
| 17 | + |
| 18 | + const map = blk: { |
| 19 | + var i: u32 = 0; |
| 20 | + var read_buf: [1024]u8 = undefined; |
| 21 | + |
| 22 | + const first_line = (try in_stream.readUntilDelimiterOrEof(&read_buf, '\n')).?; |
| 23 | + for (first_line) |point| { |
| 24 | + try map_list.append(point - '0'); |
| 25 | + i += 1; |
| 26 | + } |
| 27 | + const x_len = i; |
| 28 | + |
| 29 | + while (try in_stream.readUntilDelimiterOrEof(&read_buf, '\n')) |line| { |
| 30 | + for (first_line) |point| { |
| 31 | + try map_list.append(point - '0'); |
| 32 | + i += 1; |
| 33 | + } |
| 34 | + } |
| 35 | + const y_len = i / x_len; |
| 36 | + |
| 37 | + var small_map = Map{ .map = map_list.items, .x_len = x_len, .y_len = y_len }; |
| 38 | + var map_items = try allocator.alloc(u8, 25 * x_len * y_len); |
| 39 | + var map = Map{ .map = map_items, .x_len = 5 * x_len, .y_len = 5 * y_len }; |
| 40 | + |
| 41 | + var tile_y: u8 = 0; |
| 42 | + while (tile_y < 5) : (tile_y += 1) { |
| 43 | + var tile_x: u8 = 0; |
| 44 | + while (tile_x < 5) : (tile_x += 1) { |
| 45 | + var y: u32 = 0; |
| 46 | + while (y < y_len) : (y += 1) { |
| 47 | + var x: u32 = 0; |
| 48 | + while (x < x_len) : (x += 1) { |
| 49 | + const original: u8 = small_map.get(x, y); |
| 50 | + const val: u8 = (original - 1 + tile_x + tile_y) % 9 + 1; |
| 51 | + map.set(tile_x * x_len + x, tile_y * y_len + y, val); |
| 52 | + } |
| 53 | + } |
| 54 | + } |
| 55 | + } |
| 56 | + break :blk map; |
| 57 | + }; |
| 58 | + defer allocator.free(map.map); |
| 59 | + |
| 60 | + const len = map.map.len; |
| 61 | + |
| 62 | + const inf = std.math.maxInt(u32); |
| 63 | + |
| 64 | + var dist: []u32 = try allocator.alloc(u32, len); |
| 65 | + defer allocator.free(dist); |
| 66 | + |
| 67 | + var q = std.PriorityQueue(u64).init(allocator, compare); |
| 68 | + defer q.deinit(); |
| 69 | + |
| 70 | + { |
| 71 | + dist[0] = 0; |
| 72 | + try q.add((Vertex{ .v = 0, .dist = 0 }).toLong()); |
| 73 | + |
| 74 | + var v: u32 = 1; |
| 75 | + while (v < map.map.len) : (v += 1) { |
| 76 | + dist[v] = inf; |
| 77 | + try q.add((Vertex{ .v = v, .dist = std.math.maxInt(u32) }).toLong()); |
| 78 | + } |
| 79 | + } |
| 80 | + |
| 81 | + while (q.len > 0) { |
| 82 | + const u_vert = Vertex.fromLong(q.remove()); |
| 83 | + const u = u_vert.v; |
| 84 | + if (u == len - 1) { |
| 85 | + break; |
| 86 | + } |
| 87 | + |
| 88 | + const ns = map.neighbors(u); |
| 89 | + for (ns.get()) |v| { |
| 90 | + const alt = dist[u] + map.map[v]; |
| 91 | + if (alt < dist[v]) { |
| 92 | + try q.update((Vertex{ .v = v, .dist = dist[v] }).toLong(), (Vertex{ .v = v, .dist = alt }).toLong()); |
| 93 | + dist[v] = alt; |
| 94 | + } |
| 95 | + } |
| 96 | + } |
| 97 | + const stdout = std.io.getStdOut().writer(); |
| 98 | + try stdout.print("{d}\n", .{dist[len - 1]}); |
| 99 | +} |
| 100 | + |
| 101 | +const Neighbors = struct { |
| 102 | + len: u8 = 0, |
| 103 | + ns: [4]u32 = undefined, |
| 104 | + |
| 105 | + fn add(self: *Neighbors, x: u32, y: u32, x_len: u32) void { |
| 106 | + self.ns[self.len] = y * x_len + x; |
| 107 | + self.len += 1; |
| 108 | + } |
| 109 | + |
| 110 | + fn get(self: Neighbors) []const u32 { |
| 111 | + return self.ns[0..self.len]; |
| 112 | + } |
| 113 | +}; |
| 114 | + |
| 115 | +const Vertex = struct { |
| 116 | + v: u32, |
| 117 | + dist: u32, |
| 118 | + |
| 119 | + fn toLong(self: Vertex) u64 { |
| 120 | + var x: u64 = @as(u64, self.dist) << 32; |
| 121 | + x += self.v; |
| 122 | + return x; |
| 123 | + } |
| 124 | + |
| 125 | + fn fromLong(x: u64) Vertex { |
| 126 | + const dist_mask: u64 = 0xFFFFFFFF00000000; |
| 127 | + const v = @intCast(u32, x & ~dist_mask); |
| 128 | + const dist = @intCast(u32, (x & dist_mask) >> 32); |
| 129 | + return Vertex{ .v = v, .dist = dist }; |
| 130 | + } |
| 131 | +}; |
| 132 | + |
| 133 | +fn compare(a: u64, b: u64) std.math.Order { |
| 134 | + return std.math.order(a, b); |
| 135 | +} |
| 136 | + |
| 137 | +const Map = struct { |
| 138 | + map: []u8, |
| 139 | + x_len: u32, |
| 140 | + y_len: u32, |
| 141 | + |
| 142 | + fn set(self: *Map, x: u32, y: u32, val: u8) void { |
| 143 | + self.map[y * self.x_len + x] = val; |
| 144 | + } |
| 145 | + |
| 146 | + fn get(self: Map, x: u32, y: u32) u8 { |
| 147 | + return self.map[y * self.x_len + x]; |
| 148 | + } |
| 149 | + |
| 150 | + fn neighbors(self: Map, i: u32) Neighbors { |
| 151 | + const x_len = self.x_len; |
| 152 | + const y_len = self.y_len; |
| 153 | + const x = i % x_len; |
| 154 | + const y = i / x_len; |
| 155 | + var ns = Neighbors{}; |
| 156 | + |
| 157 | + if (x > 0) { |
| 158 | + ns.add(x - 1, y, x_len); |
| 159 | + } |
| 160 | + if (x + 1 < x_len) { |
| 161 | + ns.add(x + 1, y, x_len); |
| 162 | + } |
| 163 | + if (y > 0) { |
| 164 | + ns.add(x, y - 1, x_len); |
| 165 | + } |
| 166 | + if (y + 1 < y_len) { |
| 167 | + ns.add(x, y + 1, x_len); |
| 168 | + } |
| 169 | + |
| 170 | + return ns; |
| 171 | + } |
| 172 | + |
| 173 | + fn print(self: Map) void { |
| 174 | + var y: u32 = 0; |
| 175 | + while (y < self.y_len) : (y += 1) { |
| 176 | + var x: u32 = 0; |
| 177 | + while (x < self.x_len) : (x += 1) { |
| 178 | + const val = self.get(x, y); |
| 179 | + const c: u8 = if (val == 0) '-' else val + '0'; |
| 180 | + std.debug.print("{c}", .{c}); |
| 181 | + } |
| 182 | + std.debug.print("\n", .{}); |
| 183 | + } |
| 184 | + std.debug.print("\n", .{}); |
| 185 | + } |
| 186 | +}; |
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