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const std = @import("std");
const example = @embedFile("example");
const input = @embedFile("input");
pub fn main() anyerror!void {
var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
defer arena.deinit();
const allocator = arena.allocator();
try std.testing.expectEqual(try solve(example, allocator), 8);
const result = try solve(input, allocator);
try std.io.getStdOut().writer().print("{}\n", .{result});
}
fn solve(puzzle: []const u8, allocator: std.mem.Allocator) !u64 {
var it = std.mem.tokenize(u8, puzzle, "\n");
var heights = std.ArrayList(std.ArrayList(u8)).init(allocator);
var scenic = std.ArrayList(std.ArrayList(u64)).init(allocator);
// process input
var line = it.next() orelse unreachable;
const width = line.len;
while (true) {
var h = try heights.addOne();
var v = try scenic.addOne();
h.* = try std.ArrayList(u8).initCapacity(allocator, width);
v.* = try std.ArrayList(u64).initCapacity(allocator, width);
try h.*.writer().writeAll(line);
var i: usize = 0;
while (i < width) : (i += 1) {
v.*.appendAssumeCapacity(0);
}
if (it.next()) |l| {
line = l;
} else {
break;
}
}
const lastX = width - 1;
const lastY = heights.items.len - 1;
// init first and last lines edges
var x: usize = 1;
while (x < width - 1) : (x += 1) {
scenic.items[0].items[x] = 0;
scenic.items[lastY].items[x] = 0;
}
// calculate scenic scores tree by tree
var tot: usize = 0;
var y: usize = 1;
while (y < lastY) : (y += 1) {
x = 1;
while (x < lastX) : (x += 1) {
const max = heights.items[y].items[x];
// look right
var sr: usize = 1; // scenic score to the right
var i: usize = x + 1;
while (i < lastX) : (i += 1) {
if (heights.items[y].items[i] < max) {
sr += 1;
} else {
break;
}
}
// look left
var sl: usize = 1;
i = x - 1;
while (i > 0) : (i -= 1) {
if (heights.items[y].items[i] < max) {
sl += 1;
} else {
break;
}
}
// look down
var sd: usize = 1;
i = y + 1;
while (i < lastY) : (i += 1) {
if (heights.items[i].items[x] < max) {
sd += 1;
} else {
break;
}
}
// look up
var su: usize = 1;
i = y - 1;
while (i > 0) : (i -= 1) {
if (heights.items[i].items[x] < max) {
su += 1;
} else {
break;
}
}
const score = sr * sl * sd * su;
if (score > tot) {
tot = score;
}
}
}
return tot;
}
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