75 lines
2.7 KiB
Zig
75 lines
2.7 KiB
Zig
const std = @import("std");
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pub fn day2pt1(ranges: []const u8) !usize {
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var i = std.mem.splitScalar(u8, ranges, ',');
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var sum: usize = 0;
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while (i.next()) |range| {
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var j = std.mem.splitScalar(u8, range, '-');
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const range_start = try std.fmt.parseInt(usize, j.next().?, 10);
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const range_end = try std.fmt.parseInt(usize, j.next().?, 10);
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var k = range_start;
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const max_len = 32;
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var buf: [max_len]u8 = undefined;
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while (k <= range_end) {
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const current_id = try std.fmt.bufPrint(&buf, "{d}", .{k});
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if (current_id.len % 2 == 0) {
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const half = current_id.len / 2;
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if (std.mem.eql(u8, current_id[0..half], current_id[half..current_id.len])) {
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sum += k;
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}
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}
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k += 1;
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}
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}
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return sum;
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}
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pub fn day2pt2(ranges: []const u8) !usize {
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var i = std.mem.splitScalar(u8, ranges, ',');
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var sum: usize = 0;
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while (i.next()) |range| {
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var j = std.mem.splitScalar(u8, range, '-');
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const range_start = try std.fmt.parseInt(usize, j.next().?, 10);
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const range_end = try std.fmt.parseInt(usize, j.next().?, 10);
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var k = range_start;
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const max_len = 32;
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var buf: [max_len]u8 = undefined;
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while (k <= range_end) {
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const current_id = try std.fmt.bufPrint(&buf, "{d}", .{k});
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const len = current_id.len;
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var found = false;
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// Try all possible substring lengths that divide the length - should be made more efficient （＞人＜；）
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for (1..len / 2 + 1) |sub_len| {
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if (len % sub_len != 0) continue;
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const repeats = len / sub_len;
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if (repeats < 2) continue;
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const sub = current_id[0..sub_len];
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var valid = true;
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for (1..repeats) |r| {
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if (!std.mem.eql(u8, sub, current_id[r * sub_len .. (r + 1) * sub_len])) {
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valid = false;
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break;
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}
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}
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if (valid) {
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found = true;
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break;
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}
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}
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if (found) {
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sum += k;
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}
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k += 1;
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}
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}
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return sum;
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}
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test "Day 2 example testing" {
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const example_input = "11-22,95-115,998-1012,1188511880-1188511890,222220-222224,1698522-1698528,446443-446449,38593856-38593862,565653-565659,824824821-824824827,2121212118-2121212124";
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try std.testing.expectEqual(try day2pt1(example_input), 1227775554);
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try std.testing.expectEqual(try day2pt2(example_input), 4174379265);
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}
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