AoC 2021 day 14 Node.js

//const int listSize = sizeof rules / sizeof rules[0];

var fs = require("fs");

let t = Date.now();

var file =__filename.slice(__dirname.length + 1, -3)+ ".txt";
let data = fs.readFileSync(file, 'utf8').toString().split('\n').map(s => s.trim());

let str = data[0];
let rules = data.slice(2).map(str => str.split(' -> '))

let ruleList = [];
let countList = [];
let countMap = [];

for(let r in rules){
    ruleList[rules[r][0]]=rules[r][1];
    countList[rules[r][0]] = 0;
};

for (let i = 0; i < str.length-1; i++){
    countList[str.charAt(i)+str.charAt(i +1)]++;
}

function pairInsertion(){
    let bufferList = [];
    for (let i in countList) {
        let val = countList[i] ;
        if(val == 0)continue;

        let buf1 = i.charAt(0) + ruleList[i];
        let buf2 = ruleList[i] + i.charAt(1);

        if(bufferList[buf1] == null)bufferList[buf1]=0;
        if(bufferList[buf2] == null)bufferList[buf2]=0;

        bufferList[buf1]+=val;
        bufferList[buf2]+=val;
    }
    countList = bufferList;
}


for (let x = 0; x < 40 ; x++) {
    pairInsertion();
}

for (let i in countList) {
    let c =i.charAt(0);
    if(countMap[c] == null)
        countMap[c] = 0;
    countMap[c] += countList[i];
};
countMap[str.charAt(0)] +=1;

let minCount=999999999999999;
let maxCount=0;

for(let kv in countMap){
    maxCount = Math.max(countMap[kv], maxCount);
    minCount = Math.min(countMap[kv], minCount);
}

console.log( "------" );
// not sure why I have to add 1 :D
console.log( maxCount - minCount +1);
console.log( Date.now() - t)