97 lines
2.7 KiB
Zig
97 lines
2.7 KiB
Zig
const std = @import("std");
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// This one isn't as commented. Sorry for that.
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pub fn main() void {
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const input = @embedFile("input");
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var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
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defer arena.deinit();
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const allocator = arena.allocator();
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var iter = std.mem.split(u8, input[0 .. input.len - 1], "\n");
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const grid = iterCollapse([]const u8, &iter, allocator) catch unreachable;
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var nVisible: usize = 0;
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var bestPoints: usize = 0;
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// For each cell in the grid
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for (grid) |row, y| {
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for (row) |cell, x| {
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var cellVisible: bool = false;
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var cellPoints: usize = 1;
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defer {
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if (cellVisible) nVisible += 1;
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if (cellPoints > bestPoints) bestPoints = cellPoints;
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}
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// Look from the left
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var i: usize = x;
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var dirPoints: usize = 0;
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while (i > 0) : (i -= 1) {
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dirPoints += 1;
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if (grid[y][i - 1] >= cell) break;
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} else {
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cellVisible = true;
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}
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cellPoints *= dirPoints;
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// Look from the right
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i = x + 1;
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dirPoints = 0;
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while (i < grid[0].len) : (i += 1) {
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dirPoints += 1;
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if (grid[y][i] >= cell) break;
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} else {
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cellVisible = true;
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}
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cellPoints *= dirPoints;
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// Look from the top
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i = y;
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dirPoints = 0;
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while (i > 0) : (i -= 1) {
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dirPoints += 1;
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if (grid[i - 1][x] >= cell) break;
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} else {
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cellVisible = true;
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}
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cellPoints *= dirPoints;
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// Look from the bottom
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i = y + 1;
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dirPoints = 0;
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while (i < grid.len) : (i += 1) {
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dirPoints += 1;
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if (grid[i][x] >= cell) break;
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} else {
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cellVisible = true;
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}
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cellPoints *= dirPoints;
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}
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}
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print("Part 1: {}\n", .{nVisible});
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print("Part 2: {}\n", .{bestPoints});
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}
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// -------------------- UTIL --------------------
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pub fn print(comptime fmt: []const u8, args: anytype) void {
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std.io.getStdOut().writer().print(fmt, args) catch unreachable;
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}
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pub fn iterCollapse(comptime T: type, iter: anytype, allocator: std.mem.Allocator) ![]T {
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var vector = std.ArrayList(T).init(allocator);
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if (!@hasDecl(@TypeOf(iter.*), "next")) {
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@compileError("Cannot collapse type " ++ @typeName(@TypeOf(iter.*)) ++ ". No .next() method.");
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}
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while (@field(iter.*, "next")()) |item| {
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try vector.append(item);
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}
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return vector.items;
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}
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