day04: solve

Add a few util functions now that I'm getting sick of typing
std.mem.splitScalar.

src/util.zig

@@ -1,4 +1,37 @@
 const std = @import("std");
+const mem = std.mem;
 
 var gpa_impl = std.heap.GeneralPurposeAllocator(.{}){};
+/// General purpose allocator.
 pub const gpa = gpa_impl.allocator();
+
+pub const ParseIntsOptions = struct {
+    base: u8 = 10,
+    sep: u8 = ' ',
+};
+
+/// Parses separated integers. Sequential separators are treated as one. Caller owns memory.
+pub fn parseIntsScalar(comptime T: type, alloc: std.mem.Allocator, input: []const u8, opts: ParseIntsOptions) ![]T {
+    var items = std.ArrayList(T).init(alloc);
+    errdefer items.deinit();
+
+    var it = split(input, opts.sep);
+    while (it.next()) |i| {
+        if (i.len == 0) continue;
+        try items.append(try std.fmt.parseInt(T, i, opts.base));
+    }
+    return try items.toOwnedSlice();
+}
+
+/// Shortcut to splitScalar with a byte buffer.
+pub fn split(buffer: []const u8, sep: u8) mem.SplitIterator(u8, .scalar) {
+    return mem.splitScalar(u8, buffer, sep);
+}
+
+pub fn splitLines(buffer: []const u8) mem.SplitIterator(u8, .scalar) {
+    return split(buffer, '\n');
+}
+
+pub fn splitSpace(buffer: []const u8) mem.SplitIterator(u8, .scalar) {
+    return split(buffer, ' ');
+}