[TASK] Solved Day 3

functions/src/day3.ts

@@ -0,0 +1,62 @@
+import Utils from "./utils";
+
+class Day3 {
+
+  public static part1(input: string[]): number {
+
+    let sums = Utils.zeroes(input[0].length);
+
+    for (let value of input) {
+      for (let i = 0; i < value.length; i++) {
+        if (value[i] === "1") {
+          sums[i] += 1;
+        }
+      }
+    }
+
+    const gamma = parseInt(sums.map(s => s > input.length / 2 ? "1" : "0").join(""), 2);
+    const epsilon = parseInt(sums.map(s => s <= input.length / 2 ? "1" : "0").join(""), 2);
+
+    return gamma * epsilon;
+  }
+
+  public static part2(input: string[]): number {
+
+    return this.findLifeSupportRating(input, "oxygen") * this.findLifeSupportRating(input, "CO2");
+  }
+
+  static findLifeSupportRating(input: string[], type: "oxygen" | "CO2"): number {
+
+    const bits = input[0].length;
+    let indexesLeft = input.map((v, i) => i);
+    for (let bit = 0; bit < bits; bit++) {
+
+      const onesIdxs = indexesLeft.filter(j => input[j][bit] === "1")
+      const ones = onesIdxs.length;
+
+      if (ones >= indexesLeft.length / 2) {
+        // 1 is the most common, or they are equally common
+        if (type === "oxygen") {
+          indexesLeft = onesIdxs;
+        } else {
+          indexesLeft = indexesLeft.filter(j => input[j][bit] === "0")
+        }
+      } else {
+        // 0 is the most common
+        if (type === "oxygen") {
+          indexesLeft = indexesLeft.filter(j => input[j][bit] === "0")
+        } else {
+          indexesLeft = onesIdxs;
+        }
+      }
+
+      if (indexesLeft.length === 1) {
+        return parseInt(input[indexesLeft[0]], 2);
+      }
+    }
+    throw Error("More than one number left: " + JSON.stringify(indexesLeft));
+  }
+
+}
+
+export default Day3;

functions/src/index.ts

@@ -3,6 +3,7 @@ import Utils from "./utils";
 import Day1 from "./day1";
 import {Response} from "firebase-functions";
 import Day2 from "./day2";
+import Day3 from "./day3";
 
 
 // // Start writing Firebase Functions
@@ -35,6 +36,14 @@ export const day = {
     sendResponse(response, part1, part2);
 
   }),
+  3: functions.region("europe-west1").https.onRequest((request, response) => {
+
+    const input = Utils.parseInput(request);
+    const part1 = Day3.part1(input);
+    const part2 = Day3.part2(input);
+    sendResponse(response, part1, part2);
+
+  }),
 }
 
 function sendResponse(response: Response, part1: string | number, part2: string | number) {

functions/src/utils.ts

@@ -16,6 +16,15 @@ class Utils {
   static sum(values: number[]): number {
     return values.reduce((a, b) => a + b, 0);
   }
+
+  static zeroes(length: number): number[] {
+
+    let res = [];
+    for (let i = 0; i < length; i++) {
+      res.push(0);
+    }
+    return res;
+  }
 }
 
 export default Utils;

input/day/3-example.http

@@ -0,0 +1,17 @@
+POST http://localhost:5001/advent-of-code-2021-911a8/europe-west1/day-3
+Content-Type: text/plain
+
+00100
+11110
+10110
+10111
+10101
+01111
+00111
+11100
+10000
+11001
+00010
+01010
+
+###