javascript - 改进游程编码算法

Question

我有一个关于游程编码的字符串面试问题，我的解决方案是 O(n)。有什么办法可以改进吗:

• 输入是AABBBCAAEE
• 输出假设为A2B3C1A2E2

const firstString=(str)=>{
  const arr = str.split('');
  let counter = 1;
  let result ='';
  for (let i=0; i<arr.length; i++){
    if(arr[i] === arr[i+1]){
      counter++;
    } else {
      result +=arr[i]+counter;
      counter = 1;
    }
  } return result
};
firstString('AABBBCAAEE');

Answer 1

改善这一点的一种方法是不执行拆分。字符串也是可索引的:

let firstString = (str) => {
  if (str.length <= 0) {
    return "";
  }
  const result = [];
  result.push(str[0]);
  let counter = 1;
  for (let i = 1; i < str.length; i++) {
    if (result[result.length - 1] === str[i]) {
      counter++;
    } else {
      result.push(counter, str[i]);
      counter = 1;
    }
  }
  result.push(counter);
  return result.join("");
};