Day 5

aoc-5/main.js

@@ -0,0 +1,36 @@
+let fs = require("fs");
+
+let input = fs.readFileSync("inputs.txt", "utf8").split('');
+
+function swapCase(c) {
+    return c === c.toUpperCase() ? c.toLowerCase() : c.toUpperCase();
+}
+
+function collapsePolymer(polymer) {
+    for (let i = 0; i < polymer.length; i++) {
+        let c = polymer[i];
+    
+        if (i !== polymer.length - 1 && c === swapCase(polymer[i + 1])) {
+            polymer.splice(i, 2);
+            i = Math.max(-1, i - 2);
+        }
+    }
+
+    return polymer.length;
+}
+
+
+let shortest = Math.min(... 
+    'abcdefghijklmnopqrstuvwxyz'
+    .split('')
+    .map(
+        x => collapsePolymer(
+            input.filter(
+                y => y.toUpperCase() !== x.toUpperCase()
+            )
+        )
+    )
+);
+
+console.log(`[Part 1] Polymer length: ${ collapsePolymer(input) }`);
+console.log(`[Part 2] Shortest polymer length: ${ shortest }`);