2024: Day 1 complete

2024/day1.zig

@@ -0,0 +1,49 @@
+const std = @import("std");
+const print = std.debug.print;
+
+pub fn main() !void {
+    const file = try std.fs.cwd().openFile("day1.txt", .{});
+    defer file.close();
+
+    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
+    defer std.debug.assert(gpa.deinit() == .ok);
+    const allocator = gpa.allocator();
+
+    const stat = try file.stat();
+    const input = try file.reader().readAllAlloc(allocator, stat.size);
+    defer allocator.free(input);
+
+    var l1 = std.ArrayList(i32).init(allocator);
+    var l2 = std.ArrayList(i32).init(allocator);
+    defer l1.deinit();
+    defer l2.deinit();
+
+    var lines = std.mem.tokenizeScalar(u8, input, '\n');
+    while (lines.next()) |line| {
+        var split = std.mem.tokenizeScalar(u8, line, ' ');
+        try l1.append(try std.fmt.parseInt(i32, split.next().?, 10));
+        try l2.append(try std.fmt.parseInt(i32, split.next().?, 10));
+    }
+
+    // PART 1
+    std.mem.sort(i32, l1.items, {}, std.sort.asc(i32));
+    std.mem.sort(i32, l2.items, {}, std.sort.asc(i32));
+
+    var distance: u32 = 0;
+    for (l1.items, l2.items) |item1, item2| {
+        distance += @abs(item1 - item2);
+    }
+
+    // PART 2
+    var simScore: i32 = 0;
+    for (l1.items) |item1| {
+        var count: i32 = 0;
+        for (l2.items) |item2| {
+            if (item1 == item2) count += 1;
+        }
+        simScore += item1 * count;
+    }
+
+    print("PART 1 - DISTANCE:   {d}\n", .{distance});
+    print("PART 2 - SIMILARITY: {d}\n", .{simScore});
+}