Finish day02, part 2

src/days/day02.zig

@@ -3,5 +3,92 @@ const std = @import("std");
 pub const title = "Day 02";
 
 pub fn run(_: std.mem.Allocator) !void {
+    const input = std.mem.trim(u8, @embedFile("./input/day02.txt"), &std.ascii.whitespace);
+    //const input =
+    //    \\11-22,95-115,998-1012,1188511880-1188511890,222220-222224,1698522-1698528,446443-446449,38593856-38593862,565653-565659,824824821-824824827,2121212118-2121212124
+    //    ;
+    var ranges = std.mem.tokenizeScalar(u8, input, ',');
+
+    var accumulator: u64 = 0;
+
+    while (ranges.next()) |range| {
+        var components = std.mem.tokenizeScalar(u8, range, '-');
+
+        const start_s = components.next() orelse continue;
+        const end_s = components.next() orelse continue;
+
+        const start = try std.fmt.parseUnsigned(u64, start_s, 10);
+        const end = try std.fmt.parseUnsigned(u64, end_s, 10);
+
+        std.debug.print("{d} to {d}\n", .{start, end});
+        try processRange(&accumulator, start, end);
+    }
+
+    var buffer: [64]u8 = undefined;
+    var stdout_writer = std.fs.File.stdout().writer(&buffer);
+    const stdout = &stdout_writer.interface;
+
+    try stdout.print("{d}\n", .{accumulator});
+
+    try stdout.flush();
+}
+
+fn processRange(accumulator: *u64, start: u64, end: u64) !void {
+    for (start..end+1) |id| {
+        std.debug.print("-- Checking {d} --\n", .{id});
+
+        // IDs smaller than 10 cannot possibly have repeated digits
+        if (id / 10 == 0) {
+            std.debug.print("Skipping {d}\n", .{id});
+            continue;
+        }
+
+        const len = getLen(id);
+        inner: for (2..len + 1) |divisor| {
+            if (len % divisor != 0) continue;
+
+            std.debug.print("divisor = {d}\n", .{divisor});
+
+            const offset = len / divisor;
+
+            std.debug.print("offset = {d}\n", .{offset});
+
+            for (0..offset) |i| {
+                const a = getDigit(id, i);
+                std.debug.print("a = {d}\n", .{a});
+                for (1..divisor) |n| {
+                    const b = getDigit(id, i + offset * n);
+                    std.debug.print("b = {d}\n", .{b});
+                    if (a != b) {
+                        continue :inner;
+                    }
+                }
+            }
+
+            // If we get here, it means id is a valid cadidate
+            std.debug.print("result = {d}\n", .{id});
+            accumulator.* += id;
+            break;
+        }
+    }
+}
+
+fn getDigit(x: u64, n: usize) u8 {
+    var new_x = x;
+    for (0..n) |_| {
+        new_x /= 10;
+    }
+    return @intCast(new_x % 10);
+}
+
+fn getLen(x: u64) usize {
+    var new_x = x;
+    var n: usize = 0;
+    while (true) {
+        n += 1;
+        new_x /= 10;
+        if (new_x == 0) break;
+    }
+    return n;
 }
 

src/days/input/day02.txt

@@ -0,0 +1 @@
+52500467-52574194,655624494-655688785,551225-576932,8418349387-8418411293,678-1464,33-79,74691-118637,8787869169-8787890635,9898977468-9899009083,548472423-548598890,337245835-337375280,482823-543075,926266-991539,1642682920-1642753675,3834997-3940764,1519-2653,39697698-39890329,3-21,3251796-3429874,3467-9298,26220798-26290827,80-124,200638-280634,666386-710754,21329-64315,250-528,9202893-9264498,819775-903385,292490-356024,22-32,2663033-2791382,133-239,56514707-56704320,432810-458773,4949427889-4949576808