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day4.zig
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day4.zig
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const std = @import("std");
const mem = std.mem;
const ArrayList = std.ArrayList;
const math = @cImport({
@cInclude("math.h");
});
const dprint = std.debug.print;
var gpa = std.heap.GeneralPurposeAllocator(.{}){};
const child_allocator = gpa.allocator();
const ALLOC_SIZE = 1e5;
const FILENAME = "./input.txt";
fn split_lines(allocator: mem.Allocator, filename: []const u8) ![][]u8 {
const file = try std.fs.cwd().openFile(filename, .{});
const content = try file.reader().readAllAlloc(child_allocator, ALLOC_SIZE);
var rsz: u32 = 0;
var csz: u32 = 0;
var temp: u32 = 0;
for (content) |c| {
if (c == '\n') {
csz = @max(temp, csz);
temp = 0;
rsz += 1;
} else temp += 1;
}
var input = try allocator.alloc([]u8, rsz);
var idx: u32 = 0;
var cdx: u32 = 0;
while (idx < rsz) : (idx += 1) {
input[idx] = try allocator.alloc(u8, csz);
var jdx: u32 = 0;
while (jdx <= csz) : (jdx += 1) {
if (content[cdx] != '\n') {
input[idx][jdx] = content[cdx];
}
cdx += 1;
}
}
return input;
}
fn part2(allocator: mem.Allocator, input: [][]const u8) !void {
const sz = input.len;
// create an array on stack with default value of 1 for size 10
// var wc_input: [10]u32 = .{1} * 10;
var wc_input = try child_allocator.alloc(u32, sz); // because sz is not known at compile time
@memset(wc_input, 1);
for (input, 0..) |line, idx| {
var card_iter = mem.splitSequence(u8, line, ": ");
_ = card_iter.next().?;
var card_nums = card_iter.next().?;
var split_iter = mem.splitSequence(u8, card_nums, " | ");
// use tokenize because there can be multiple spaces between number (because of padding)
var set1 = mem.tokenizeAny(u8, split_iter.next().?, " ");
var set2 = mem.tokenizeAny(u8, split_iter.next().?, " ");
var arr1 = ArrayList(u32).init(allocator);
defer arr1.deinit();
while (set1.next()) |str| {
const num = try std.fmt.parseInt(u32, str, 10);
try arr1.append(num);
}
var arr2 = ArrayList(u32).init(allocator);
defer arr2.deinit();
while (set2.next()) |str| {
const num = try std.fmt.parseInt(u32, str, 10);
try arr2.append(num);
}
var matched: u32 = 0;
for (arr2.items) |num2| {
for (arr1.items) |num1| {
if (num2 == num1) {
matched += 1;
}
}
}
dprint("idx: {}, matched: {}\n", .{ idx, matched });
var cidx: u32 = @as(u32, @intCast(idx)) + 1;
while (cidx <= idx + matched) : (cidx += 1) {
wc_input[cidx] += (1 * wc_input[idx]);
}
for (wc_input) |c| {
dprint("{} ", .{c});
}
dprint("\n", .{});
}
var sum: u32 = 0;
for (wc_input) |c| {
sum += c;
}
dprint("sum: {}\n", .{sum});
}
fn part1(allocator: mem.Allocator, input: [][]const u8) !void {
var sum: u32 = 0;
for (input) |line| {
var card_iter = mem.splitSequence(u8, line, ": ");
_ = card_iter.next().?;
var card_nums = card_iter.next().?;
var split_iter = mem.splitSequence(u8, card_nums, " | ");
// use tokenize because there can be multiple space before number (due to padding in input)
var set1 = mem.tokenizeAny(u8, split_iter.next().?, " ");
var set2 = mem.tokenizeAny(u8, split_iter.next().?, " ");
var arr1 = ArrayList(u32).init(allocator);
defer arr1.deinit();
while (set1.next()) |str| {
const num = try std.fmt.parseInt(u32, str, 10);
try arr1.append(num);
}
var arr2 = ArrayList(u32).init(allocator);
defer arr2.deinit();
while (set2.next()) |str| {
const num = try std.fmt.parseInt(u32, str, 10);
try arr2.append(num);
}
var times: u32 = 0;
var card_sum: u32 = 0;
for (arr2.items) |num2| {
for (arr1.items) |num1| {
if (num1 == num2) {
card_sum = @intFromFloat(math.pow(2, @floatFromInt(times)));
dprint("card_sum: {}\n", .{card_sum});
times += 1;
}
}
}
sum += card_sum;
dprint("line: {s} | sum: {}\n", .{ line, sum });
}
dprint("sum: {}\n", .{sum});
}
pub fn main() !void {
var arena = std.heap.ArenaAllocator.init(child_allocator);
var allocator = arena.allocator();
defer arena.deinit();
const input = try split_lines(allocator, FILENAME);
for (input) |line| {
dprint("{s}\n", .{line});
}
// try part1(allocator, input);
try part2(allocator, input);
}