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const std = @import("std");
const mecha = @import("mecha");
const print = std.debug.print;
pub fn solve(part: []u8, buffer: []u8, allocator: std.mem.Allocator) !void {
var lookup: [256]std.ArrayList(std.meta.Tuple(&.{ i32, i32 })) = undefined;
for (&lookup) |*element| {
element.* = std.ArrayList(std.meta.Tuple(&.{ i32, i32 })).init(allocator);
errdefer element.*.deinit();
}
var lines = std.mem.splitScalar(u8, buffer, '\n');
const width: usize = lines.next().?.len;
lines.reset();
const distinct: [][]bool = try allocator.alloc([]bool, width * width);
defer allocator.free(distinct);
for (distinct) |*r| {
r.* = try allocator.alloc(bool, width);
@memset(r.*, false);
}
if (std.mem.eql(u8, part, "1")) {
try part1(&lookup, distinct, &lines, width);
} else {
try part2(&lookup, distinct, &lines, width);
}
for (&lookup) |*element| {
element.*.deinit();
}
for (distinct) |r| {
allocator.free(r);
}
}
fn part1(lookup: *[256]std.ArrayList(std.meta.Tuple(&.{ i32, i32 })), distinct: [][]bool, lines: *std.mem.SplitIterator(u8, .scalar), width: usize) !void {
var row: i32 = 0;
var total_distinct: usize = 0;
while (lines.next()) |line| : (row += 1) {
if (line.len == 0) break;
var col: i32 = 0;
for (line) |item| {
if (item == '.' or item == '#') {
col += 1;
continue;
}
for (lookup[item].items) |antenna| {
const diffr = row - antenna[0];
const diffc = col - antenna[1];
const newr1 = antenna[0] - diffr;
const newc1 = antenna[1] - diffc;
if (newr1 >= 0 and newc1 >= 0 and newc1 < width and !distinct[@intCast(newr1)][@intCast(newc1)]) {
distinct[@intCast(newr1)][@intCast(newc1)] = true;
total_distinct += 1;
}
const newr2 = row + diffr;
const newc2 = col + diffc;
if (newr2 < width and newc2 >= 0 and newc2 < width and !distinct[@intCast(newr2)][@intCast(newc2)]) {
distinct[@intCast(newr2)][@intCast(newc2)] = true;
total_distinct += 1;
}
}
try lookup[item].append(.{ row, col });
col += 1;
}
}
print("{d}\n", .{total_distinct});
}
fn part2(lookup: *[256]std.ArrayList(std.meta.Tuple(&.{ i32, i32 })), distinct: [][]bool, lines: *std.mem.SplitIterator(u8, .scalar), width: usize) !void {
var row: i32 = 0;
var total_distinct: usize = 0;
while (lines.next()) |line| : (row += 1) {
if (line.len == 0) break;
var col: i32 = 0;
for (line) |item| {
if (item == '.' or item == '#') {
col += 1;
continue;
}
for (lookup[item].items) |antenna| {
const diffr = row - antenna[0];
const diffc = col - antenna[1];
var newr1 = antenna[0];
var newc1 = antenna[1];
while (newr1 >= 0 and newc1 >= 0 and newc1 < width) {
if (!distinct[@intCast(newr1)][@intCast(newc1)]) {
distinct[@intCast(newr1)][@intCast(newc1)] = true;
total_distinct += 1;
}
newr1 -= diffr;
newc1 -= diffc;
}
var newr2 = row;
var newc2 = col;
while (newr2 < width and newc2 >= 0 and newc2 < width) {
if (!distinct[@intCast(newr2)][@intCast(newc2)]) {
distinct[@intCast(newr2)][@intCast(newc2)] = true;
total_distinct += 1;
}
newr2 += diffr;
newc2 += diffc;
}
}
try lookup[item].append(.{ row, col });
col += 1;
}
}
print("{d}\n", .{total_distinct});
}
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