Adds optimized part one

Author: romellem

2019/16/part-one-optimized.js

@@ -0,0 +1,38 @@
+// Performs much better for larger inputs because:
+// - We don't generate long arrays for patterns
+const { input } = require('./input');
+
+const base_pattern = [0, 1, 0, -1];
+let current = input;
+
+for (let phase = 1; phase <= 100; phase++) {
+	let new_arr = [];
+	for (let n = 0; n < current.length; n++) {
+		let sum = 0;
+
+		let index = 0;
+		let position = n + 1;
+		for (let i = 0; i < current.length; i++) {
+			position--;
+			if (position <= 0) {
+				position = n + 1;
+				index = (index + 1) % base_pattern.length;
+			}
+
+			let v = current[i];
+			let scalar = base_pattern[index];
+			let new_val = v * scalar;
+
+			sum += new_val;
+		}
+
+		let last_digit = Math.abs(sum % 10);
+
+		new_arr.push(last_digit);
+	}
+
+	current = new_arr;
+}
+
+let first_eight_digits = current.slice(0, 8).join('');
+console.log(first_eight_digits);