Javascript
More bruteforcing! There are probably better ways to do this but I'm happy enough with this lol.
Solution
You can replace the require('fs') on the first line with the input and run it in your browser console as well.
const input = require('fs').readFileSync('input-day2.txt', 'utf-8');
let idsPart1 = [];
let idsPart2 = [];
input.split(',').forEach(range => {
const [start, end] = range.split('-').map(v => parseInt(v, 10));
let cursor = start;
while (cursor <= end) {
const cursorString = cursor.toString(10);
// part 1 check
let halfLength = Math.floor(cursorString.length / 2);
let left = cursorString.slice(0, halfLength);
let right = cursorString.slice(halfLength, cursorString.length);
if (left === right) {
idsPart1.push(cursor);
}
// part 2 check
let sequenceLength = 1;
while (sequenceLength <= halfLength) {
const sequence = cursorString.slice(0, sequenceLength);
let builtString = sequence;
while (builtString.length < cursorString.length) {
builtString = `${builtString}${sequence}`;
}
if (builtString === cursorString) {
idsPart2.push(cursor);
break;
}
sequenceLength += 1;
}
cursor += 1;
}
})
const answer1 = idsPart1.flat().reduce((acc, cur) => acc += cur, 0);
const answer2 = idsPart2.flat().reduce((acc, cur) => acc += cur, 0);
console.log(`Part 1 Answer: ${answer1}`);
console.log(`Part 2 Answer: ${answer2}`);