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79 lines
2.1 KiB
Zig
79 lines
2.1 KiB
Zig
const std = @import("std");
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pub fn main() !void {
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const content = @embedFile("data.txt");
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var lines = std.mem.split(u8, content, "\n");
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var gpa = std.heap.GeneralPurposeAllocator(.{}){};
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const allocator = gpa.allocator();
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var list = std.ArrayList(std.ArrayList(i32)).init(allocator);
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defer list.deinit();
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while (lines.next()) |line| {
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if (line.len == 0) {
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break;
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}
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var history = std.ArrayList(i32).init(allocator);
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var nums = std.mem.split(u8, line, " ");
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while (nums.next()) |num| {
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const parsed = try std.fmt.parseInt(i32, num, 10);
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try history.append(parsed);
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}
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try list.append(history);
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}
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var part1: i32 = 0;
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var part2: i32 = 0;
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for (list.items) |history| {
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var derived = std.ArrayList(std.ArrayList(i32)).init(allocator);
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try derived.append(history);
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var cur = history;
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while (true) {
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var d = try derive(cur, allocator);
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try derived.append(d);
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cur = d;
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var allZero = true;
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for (d.items) |item| {
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if (item != 0) {
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allZero = false;
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}
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}
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if (allZero) {
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break;
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}
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}
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var newItem: i32 = 0;
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var newItem2: i32 = 0;
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for (derived.items, 0..) |_, j| {
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// part 1
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const idx = derived.items.len - j - 1;
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const lastItem = derived.items[idx].getLast();
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newItem = lastItem + newItem;
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// part 2
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const firstItem = derived.items[idx].items[0];
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newItem2 = firstItem - newItem2;
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}
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part1 += newItem;
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part2 += newItem2;
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}
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std.debug.print("Part 1: {d}\n", .{part1});
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std.debug.print("Part 2: {d}\n", .{part2});
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}
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fn derive(history: std.ArrayList(i32), allocator: std.mem.Allocator) !std.ArrayList(i32) {
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var list = std.ArrayList(i32).init(allocator);
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for (0..history.items.len - 1) |idx| {
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try list.append(history.items[idx + 1] - history.items[idx]);
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}
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return list;
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}
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