aoc/2020/18/part1.js

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JavaScript
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2020-12-18 14:59:39 +00:00
const fs = require('fs');
const expressions = fs.readFileSync('./input.txt', 'utf-8').split('\n');
function calc (expression) {
// if it's just a number, do nothing
if (!isNaN(Number(expression))) { Number(expression) }
// if there's brackets, do that first
while (expression.match(/\(/)){
expression = expression.replace(/\([^()]+\)/, match =>
calc (match.slice(1, match.length-1))
)
}
// do all the calculations until it's just a number
while (isNaN(Number(expression))) {
expression = expression.replace(/(\d+) ([+*]) (\d+)/, (match, a, op, b) =>
op == '+' ? parseInt(a) + parseInt(b) : parseInt(a) * parseInt(b)
)
}
return Number(expression)
}
let runningTotal = 0
for (expression of expressions) {
runningTotal += calc (expression)
}
console.log(runningTotal)