[Day 25](https://adventofcode.com/2018/day/25)[Day 18](https://adventofcode.com/2018/day/18)[Day 21](https://adventofcode.com/2018/day/21)Day 19[Day 16](https://adventofcode.com/2018/day/16)[Day 14](https://adventofcode.com/2018/day/14)[Day 13](https://adventofcode.com/2018/day/13)[Day 12](https://adventofcode.com/2018/day/12)[Day 11](https://adventofcode.com/2018/day/11)[Day 10](https://adventofcode.com/2018/day/10)[Day 9](https://adventofcode.com/2018/day/9)[Day 8](https://adventofcode.com/2018/day/8)[Day 7](https://adventofcode.com/2018/day/7)[Day 6](https://adventofcode.com/2018/day/6)[Day 5](https://adventofcode.com/2018/day/5)[Day 4](https://adventofcode.com/2018/day/4)[Day 3](https://adventofcode.com/2018/day/3)[Day 1](https://adventofcode.com/2018/day/1)
Advent of Code: [Day 2](https://adventofcode.com/2018/day/2)
checksum = {
let hasTwo = 0;
let hasThree = 0;
for (let box of data) {
let counter = {}
for (const c of box) {
counter[c] = (counter[c] || 0) + 1;
}
const countSet = new Set(Object.values(counter));
if (countSet.has(2)) {
hasTwo++;
}
if (countSet.has(3)) {
hasThree++;
}
}
return hasTwo * hasThree;
}
commonLetters = {
let seen = new Set()
for (const box of data) {
for (let i = 0; i < box.length; i++) {
const substring = box.slice(0, i) + box.slice(i+1);
if (seen.has(`[${substring}, ${i}]`)) {
return substring;
}
seen.add(`[${substring}, ${i}]`);
}
}
return seen;
}
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