Reference passing

.gitignore

@@ -56,3 +56,4 @@ tap_history
 
 # AOC specific
 input*
+test_input*

aoc/day10_1.tap

@@ -0,0 +1,123 @@
+get_file_content(): string = {
+    file = open(args.get(0), "r");
+    content: string = file.read();
+    file.close();
+    content
+}
+
+pow2(n): int = {
+    mut res = 1;
+    for i in 0..<n {
+        res = res * 2;
+    }
+    res
+}
+
+solve() = {
+    content = get_file_content();
+    lines: [string] = content.split("\n").filter((l) => l.length() > 0);
+
+    mut total_presses = 0;
+
+    for line in lines {
+        parts = line.split(" ").filter((s) => s.length() > 0);
+
+        // Parse target machine state
+        // Format: [.##.]
+        diag_part = parts[0];
+        diag_len = diag_part.length();
+
+        mut target_mask = 0;
+        for i in 1..<(diag_len - 1) {
+            char = diag_part[i];
+            if char == "#" {
+                light_idx = i - 1;
+                target_mask = target_mask + pow2(light_idx);
+            }
+        }
+
+        // Parse buttons
+        // Format: (0,2) (1,3) ... until we hit {
+        mut buttons: [int] = [];
+        mut p_idx = 1;
+        mut parsing_buttons = true;
+
+        while parsing_buttons {
+            if p_idx >= parts.length() {
+                parsing_buttons = false;
+            } else {
+                part = parts[p_idx];
+                if part[0] == "{" {
+                    parsing_buttons = false;
+                } else {  // It's a button: (1,2,3)
+                    // Strip parens at 0 and length-1
+                    // built-in substring takes (string, len) params
+                    inner = part.substring(1, part.length() - 2);
+                    nums = inner.split(",");
+                    mut btn_mask = 0;
+                    for num_s in nums {
+                        if num_s.length() > 0 {
+                            idx = num_s.parse_int();
+                            btn_mask = btn_mask + pow2(idx);
+                        }
+                    }
+                    buttons.push(btn_mask);
+                    p_idx = p_idx + 1;
+                }
+            }
+        }
+
+        // --- BFS to find minimum presses ---
+        // State: current bitmask of lights
+        // Start: 0 (all lights off initially)
+        // Target: target_mask
+
+        mut q: [int] = [];
+        q.push(0);
+
+        mut dists = Map();
+        dists.insert(0, 0);
+
+        mut min_steps = -1;
+        mut head = 0;
+
+        // Optimization: check if we are already there
+        if target_mask == 0 {
+            min_steps = 0;
+        }
+
+        while min_steps == -1 {
+            // Safety break for empty queue
+            if head >= q.length() {
+                print("Error: Could not solve machine: " + line);
+                break;
+            }
+
+            curr = q[head];
+            head = head + 1;
+
+            d = dists.get(curr);
+
+            if curr == target_mask {
+                min_steps = d;
+            } else {
+                // Try pressing each button
+                for btn in buttons {
+                    // Apply button using XOR
+                    next_state = curr ^ btn;
+
+                    if !dists.has(next_state) {
+                        dists.insert(next_state, d + 1);
+                        q.push(next_state);
+                    }
+                }
+            }
+        }
+
+        total_presses = total_presses + min_steps;
+    }
+
+    print("Total minimum presses: " + total_presses.to_string());
+}
+
+solve();