❓ 打印出 1 - 10000 之间的所有对称数

// 暴力
function palindrome(num) {
  let index = 10,
    result = []
  if (num < 10) return result
  while (index < num) {
    if (index.toString().split('').reverse().join('') === index.toString()) {
      result.push(index)
      console.log(index)
    }
    index++
  }
  return result
}

palindrome(10000)

function palindrome2(num) {
  let index = 1,
    result = []
  while (index < 10) {
    let _index = 0
    // AA
    result.push('' + index + index)
    while (_index < 10) {
      // ABA
      result.push('' + index + _index + index)
      // ABBA
      result.push('' + index + _index + _index + index)
      _index++
    }
    index++
  }
  return result
}

console.log(palindrome2(10000))