Add day 12 pt 1 solution

12/12_1.js

@@ -16,6 +16,36 @@ const tests = parseInput([
     "<x=3, y=5, z=-1>",
 ]);
 
+const STEPS = 1000;
+
+for (let i = 0; i < STEPS; i++) {
+    step(input);
+}
+
+console.log(`Total energy in system is: ${calculateTotalEnergy(input)}`);
+
+/**
+ * Calculate one step of time
+ *
+ * @param {Moon[]} moons A list of moons
+ * @returns {void}
+ */
+function step(moons) {
+    for (let i = 0; i < moons.length - 1; i++) {
+        for (let j = i + 1; j < moons.length; j++) {
+            // Calculate Moon B's gravity influence on Moon A
+            const firstGravity = calculateGravity(moons[i], moons[j]);
+            // Invert the signage to represent Moon A's influence on Moon B
+            const secondGravity = firstGravity.negate();
+
+            moons[i].velocity.add(firstGravity);
+            moons[j].velocity.add(secondGravity);
+        }
+    }
+
+    moons.forEach((moon) => { moon.position.add(moon.velocity); });
+}
+
 /**
  * Find the gravitational influence two moons have on each other
  *
@@ -38,6 +68,27 @@ function calculateGravity(moonA, moonB) {
     return gravityDifference;
 }
 
+/**
+ * Calculate the total energy in the system
+ *
+ * The total energy in the system is the sum of the sum of the positional
+ * values multiplied by the sum of the velocity values.
+ *
+ * @param {Moon[]} moons The moons in the system
+ * @returns {number} The total energy in the system
+ */
+function calculateTotalEnergy(moons) {
+    let energy = 0;
+
+    for (const moon of moons) {
+        const potentialEnergy = Math.abs(moon.position.x) + Math.abs(moon.position.y) + Math.abs(moon.position.z);
+        const kineticEnergy = Math.abs(moon.velocity.x) + Math.abs(moon.velocity.y) + Math.abs(moon.velocity.z);
+        energy += potentialEnergy * kineticEnergy;
+    }
+
+    return energy;
+}
+
 /**
  * @param {string[]} inputs The day's input
  * @returns {Moon[]} An array of Moon objects