d2p1

solutions/02.ts

@@ -3,19 +3,17 @@ import { solvables } from "../main.ts";
 import type { Solvable } from "../solvable.ts";
 import { readInput } from "../utils.ts";
 
-
-// check if pattern with given width repeats in input
-const checkWindow = (width: number, input: number): boolean => {
+const checkWindow = (input: number): boolean => {
+    const width = String(input).length / 2
     const str = String(input);
-    for (let patternStart = 0; patternStart + 2 * width < str.length; patternStart += width) {
-        const leftPatIdx = [patternStart, patternStart + width]
-        const rightPatIdx = [patternStart + width, patternStart + width + width]
-        const patternRepeated = str.slice(...leftPatIdx) === str.slice(...rightPatIdx);
-        if (patternRepeated) {
-            return true;
-        }
-    }
-    return false
+
+    const leftPatIdx = [0, width]
+    const rightPatIdx = [width, width + width]
+
+    const left = str.slice(...leftPatIdx)
+    const right = str.slice(...rightPatIdx);
+
+    return left === right;
 }
 
 class DayTwo implements Solvable {
@@ -24,23 +22,17 @@ class DayTwo implements Solvable {
     public part1(): DayTwo {
         const vals: [number, number][] = this.input
             .split(",")
-            .map(range => range.split("-")
+            .map(range => range.trim().split("-")
                 .map(Number) as [number, number]);
 
         const invalid: number[] = [];
         
         for (const [start, end] of vals) {
             for (let i = start; i <= end; i++) {
-                // if the number is of odd length, it can't have a repeating pattern
-                if (String(i).length % 2 !== 0) {
-                    continue;
-                }
-                // check for patterns with increasing width but never exceeding half the length of the number
-                for (let width = 2; width <= String(i).length / 2; width++) {
-                    if (checkWindow(width, i)) {
-                        invalid.push(i);
-                        break;
-                    }
+                if (String(i).length % 2 === 1) continue
+                if (checkWindow(i)) {
+                    console.log(i)
+                    invalid.push(i);
                 }
             }
         }