day 3

Signed-off-by: Jack Bond-Preston <jackbondpreston@outlook.com>

3/3a.js

@@ -0,0 +1,29 @@
+const fs = require('fs');
+
+const data = fs.readFileSync("input.txt", "utf8").split("\n");
+const width = data[0].length;
+
+const result = data
+    .reduce((acc, val) => {
+        for (let c = 0; c < width; c++) {
+            if (val.charAt(c) === '1') {
+                acc[c] += 1;
+            }
+        }
+
+        return acc;
+    }, Array(width).fill(0))
+    .map(x => x > (data.length - 1) / 2)
+    .reduce((acc, val, index) => {
+        if (val) {
+            acc += Math.pow(2, (width - index - 1));
+        }
+
+        return acc;
+    }, 0);
+
+const epsilon = result;
+const gamma = ~result & ~(-1 << width);
+
+console.log(epsilon * gamma);
+

3/3b.js

@@ -0,0 +1,32 @@
+const fs = require('fs');
+
+const data = fs.readFileSync("input.txt", "utf8").split("\n");
+data.pop();
+const width = data[0].length;
+
+let results = [0, 0];
+let filtered;
+
+for (let x = 0; x <= 1; x++) {
+    filtered = data;
+    for (let i = 0; i < width && filtered.length > 1; i++) {
+        const numOnes = filtered
+            .reduce((acc, val) => {
+                if (val.charAt(i) === x.toString()) {
+                    acc += 1;
+                }
+                return acc;
+            }, 0);
+        
+        let keep = x.toString();
+        if (numOnes < filtered.length / 2) keep = '0';
+        if (numOnes > filtered.length / 2) keep = '1';
+
+        filtered = filtered
+            .filter(x => x.charAt(i) === keep);
+    }
+    results[x] = parseInt(filtered[0], 2);
+}
+
+
+console.log(results.reduce((x, y) => x * y));