d3p2

src/day3/index.ts

@@ -2,22 +2,56 @@ import path from 'path';
 import { readFile } from "../utils";
 
 let input = readFile(path.resolve(__dirname, 'input.txt'));
-
 const size = input[0].length;
 let bucket = Array(size).fill(0).map(x => Object.assign({}, [0, 0]));
 
-input
-    .map((x: string) => {
-        x.split('')
-            .map((c, idx: number) => {
-                if (c === '0') bucket[idx][0]++; else bucket[idx][1]++
-            })
-    })
+const toDecimal = (binary) => parseInt(binary, 2);
 
-let gamma = parseInt(bucket.map(x => x[0] < x[1] ? "0" : "1").join(""), 2)
-let eps = parseInt(bucket.map(x => x[0] < x[1] ? "1" : "0").join(""), 2)
+
+input.map((x: string) => {
+    x.split('')
+        .map((c: string, idx: number) => {
+            if (c === '0') bucket[idx][0]++; else bucket[idx][1]++
+        })
+})
+
+const MSB = bucket.map(x => x[0] < x[1] ? "0" : "1").join("");
+const LSB = bucket.map(x => x[0] < x[1] ? "1" : "0").join("");
+
+let gamma = toDecimal(MSB)
+let eps = toDecimal(LSB)
 
 const power = gamma * eps;
 
 console.log("Part 1: ", power);
 
+const getBitCrit = (array, MSB, eqValue) => {
+    let tmpArray = [...array];
+
+    for (const idx in [...Array(size).keys()]) {
+
+        let count = [0, 0];
+        let keepMe;
+
+        // Count 0/1 values
+        tmpArray.forEach((x: string) => {
+            x[idx] === "0" ? count[0]++ : count[1]++;
+        })
+
+        // Swap results if we look for the least common value
+        if (!MSB) count = [count[1], count[0]]
+
+        // Which value to keep
+        if (count[0] === count[1]) keepMe = eqValue;
+        else keepMe = count[0] < count[1] ? '1' : '0'
+
+        // Filter
+        tmpArray = tmpArray.filter((x: string) => x[idx] === keepMe)
+
+        if (tmpArray.length === 1) return tmpArray[0];
+    }
+}
+
+const oxygen = toDecimal(getBitCrit(input, true, "1"));
+const co2 = toDecimal(getBitCrit(input, false, "0"));
+console.log("Part 2: ", oxygen * co2);