day 2

day2/day2_part1.zig

@@ -0,0 +1,75 @@
+const std = @import("std");
+
+pub fn main() !void {
+    const file = try std.fs.cwd().openFile("input", .{});
+    const file_reader = file.reader();
+    defer file.close();
+
+    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
+    const ally = gpa.allocator();
+    defer _ = gpa.deinit();
+
+    var input_buf = std.ArrayListUnmanaged(u8){};
+    defer input_buf.deinit(ally);
+    var integer_buf = std.ArrayListUnmanaged(u32){};
+    defer integer_buf.deinit(ally);
+    var integer_slice = std.ArrayList(u32).init(ally);
+    defer integer_slice.deinit();
+
+    var safe_levels: u32 = 0;
+    while (true) {
+        defer input_buf.clearRetainingCapacity();
+        file_reader.streamUntilDelimiter(input_buf.writer(ally), '\n', null) catch |err| switch (err) {
+            error.EndOfStream => break,
+            else => break,
+        };
+
+        var integers = std.mem.splitSequence(u8, input_buf.items, " ");
+        const integer_count: usize = integers.rest().len;
+        try integer_buf.ensureTotalCapacity(ally, integer_count);
+
+        var asc = true;
+        var last_int: u32 = 0;
+        var diff: u32 = 0;
+        var safe: bool = true;
+
+        integers = std.mem.splitSequence(u8, input_buf.items, " ");
+        integer_slice.clearRetainingCapacity();
+        while (integers.next()) |integer| {
+            const int = std.fmt.parseInt(u32, integer, 10) catch |err| {
+                std.debug.print("Error parsing integer: {}\n", .{err});
+                continue;
+            };
+            try integer_slice.append(int);
+        }
+
+        for (integer_slice.items, 0..) |integer, i| {
+            if (i == 0) continue;
+            last_int = integer_slice.items[i - 1];
+
+            // Check diff
+            diff = if (integer > last_int) @abs(integer - last_int) else @abs(last_int - integer);
+            if (diff < 1 or diff > 3) {
+                safe = false;
+                break;
+            }
+
+            // Establish order - asc/desc
+            if (i == 1) {
+                asc = integer > last_int;
+                continue;
+            }
+
+            if ((integer > last_int) != asc) {
+                safe = false;
+                break;
+            }
+        }
+
+        if (safe) {
+            safe_levels += 1;
+        }
+    }
+
+    std.debug.print("{}\n", .{safe_levels});
+}