题解 | #合法IP#

const readline = require('readline');

const rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout
})
rl.on('line', function (line) {
  const ipArr = line.split('.')
  if (ipArr.length !== 4) {
    console.log('NO')
    return
  }
  for (let i = 0; i < ipArr.length; i++) {
    const ele = ipArr[i];
    const notNum = ele.replace(/[0-9]/g, '')
    const num = Number(ele)
    // 判断当前ip是否有值 及 将数字都替换为空，如果还存在字符，则说明不是存在额外的字符串 以及判断ip地址的范围是否越界
    if ((ele == null) || (ele == '') || notNum.length > 0 || num > 255 || num < 0) {
      console.log('NO')
      return
    }
    if (ele.length > 1 && ele[0] == '0') {
      console.log('NO')
      return
    }
  }
  console.log('YES')
})