1 files changed, 109 insertions, 0 deletions
diff --git a/src/day07.zig b/src/day07.zig
new file mode 100644
index 0000000..f06e08d
--- /dev/null
+++ b/src/day07.zig
@@ -0,0 +1,109 @@
+const std = @import("std");
+const mecha = @import("mecha");
+const print = std.debug.print;
+
+pub fn solve(part: []u8, buffer: []u8, allocator: std.mem.Allocator) !void {
+    if (std.mem.eql(u8, part, "1")) {
+        try part1(buffer, allocator);
+    } else {
+        try part2(buffer, allocator);
+    }
+}
+
+fn evaluate(test_value: usize, numbers: []const usize, index: usize) bool {
+    if (index == 0) {
+        return test_value == numbers[0];
+    }
+
+    const number = numbers[index];
+
+    const division: usize = test_value / number;
+
+    if (division * number == test_value) {
+        const b = evaluate(division, numbers, index - 1);
+        if (!b and test_value >= number and (test_value - number) % number == 0) return evaluate(test_value - number, numbers, index - 1);
+        return b;
+    } else if (test_value >= number) {
+        return evaluate(test_value - number, numbers, index - 1);
+    }
+
+    return false;
+}
+
+fn part1(buffer: []const u8, allocator: std.mem.Allocator) !void {
+    const parser = mecha.combine(.{ mecha.int(usize, .{}), mecha.string(": ").discard(), mecha.many(mecha.int(usize, .{}), .{ .separator = mecha.string(" ").discard() }) });
+    var lines = std.mem.splitScalar(u8, buffer, '\n');
+
+    var total: usize = 0;
+    while (lines.next()) |line| {
+        if (line.len == 0) break;
+
+        const parsed = try parser.parse(allocator, line);
+        const test_value = parsed.value[0];
+        const numbers: []const usize = parsed.value[1];
+
+        if (evaluate(test_value, numbers, numbers.len - 1)) {
+            total += parsed.value[0];
+        }
+        allocator.free(numbers);
+    }
+    print("{d}\n", .{total});
+}
+
+//----------------------------------------------PART 2--------------------------------------------------------
+
+fn magnitude(int2: usize) usize {
+    var count: usize = 0;
+    var temp = int2;
+    while (temp > 0) {
+        temp /= 10;
+        count += 1;
+    }
+    return std.math.pow(usize, 10, count);
+}
+
+fn evaluate2(test_value: usize, numbers: []usize, index: usize) bool {
+    if (index == 0) {
+        return test_value == numbers[0];
+    }
+
+    const number = numbers[index];
+
+    const division: usize = test_value / number;
+
+    if (division * number == test_value) {
+        const b = evaluate2(division, numbers, index - 1);
+        if (b) {
+            return true;
+        } else if (test_value >= number and (test_value - number) % number == 0 and evaluate2(test_value - number, numbers, index - 1)) return true;
+    } else if (test_value >= number and evaluate2(test_value - number, numbers, index - 1)) {
+        return true;
+    }
+
+    const base = magnitude(number);
+    if (test_value % base == number) {
+        return evaluate2(test_value / base, numbers, index - 1);
+    }
+
+    return false;
+}
+
+fn part2(buffer: []const u8, allocator: std.mem.Allocator) !void {
+    const parser = mecha.combine(.{ mecha.int(usize, .{}), mecha.string(": ").discard(), mecha.many(mecha.int(usize, .{}), .{ .separator = mecha.string(" ").discard() }) });
+    var lines = std.mem.splitScalar(u8, buffer, '\n');
+
+    var total: usize = 0;
+    while (lines.next()) |line| {
+        if (line.len == 0) break;
+
+        const parsed = try parser.parse(allocator, line);
+        const test_value = parsed.value[0];
+        const numbers: []usize = parsed.value[1];
+
+        if (evaluate2(test_value, numbers, numbers.len - 1)) {
+            total += parsed.value[0];
+        }
+        allocator.free(numbers);
+    }
+    print("{d}\n", .{total});
+}