[TASK] Solved Day 7

functions/src/day7.ts

@@ -0,0 +1,45 @@
+import Day from "./day";
+import Utils from "./utils";
+
+class Day7 implements Day {
+
+  part1(input: string[]): number | string {
+
+    const initialPositions = input[0].split(",").map(s => parseInt(s));
+    initialPositions.sort((a, b) => a - b);
+
+    // The optimal position is just the median:
+    const pos = initialPositions[Math.floor(initialPositions.length / 2)];
+
+    // So we calculate the fuel usage in that position
+    return Utils.sum(initialPositions.map(p => Math.abs(pos - p)));
+  }
+
+
+  part2(input: string[]): number | string {
+
+    const initialPositions = input[0].split(",").map(s => parseInt(s));
+    const min = Math.min(...initialPositions);
+    const max = Math.max(...initialPositions);
+
+    const fuelUsage = Array(max + 1);
+    let lastFuel = 0;
+    for (let i = 0; i < fuelUsage.length; i++) {
+      fuelUsage[i] = lastFuel + i;
+      lastFuel = fuelUsage[i];
+    }
+
+    let bestFoundFuelCost = Number.MAX_SAFE_INTEGER;
+    for (let pos = min; pos < max; pos++) {
+
+      const fuelCost = Utils.sum(initialPositions.map(p => fuelUsage[Math.abs(pos - p)]));
+      if (fuelCost < bestFoundFuelCost) {
+        bestFoundFuelCost = fuelCost;
+      }
+    }
+
+    return bestFoundFuelCost;
+  }
+}
+
+export default Day7;

functions/src/index.ts

@@ -8,6 +8,7 @@ import Day3 from "./day3";
 import Day4 from "./day4";
 import Day5 from "./day5";
 import Day6 from "./day6";
+import Day7 from "./day7";
 
 
 // // Start writing Firebase Functions
@@ -30,6 +31,7 @@ export const day = {
   4: functions.region("europe-west1").https.onRequest((request, response) => { processDay(new Day4(), request, response) }),
   5: functions.region("europe-west1").https.onRequest((request, response) => { processDay(new Day5(), request, response) }),
   6: functions.region("europe-west1").https.onRequest((request, response) => { processDay(new Day6(), request, response) }),
+  7: functions.region("europe-west1").https.onRequest((request, response) => { processDay(new Day7(), request, response) }),
 
 }