题解 | 【模板】队列操作

const rl = require("readline").createInterface({ input: process.stdin });

var iter = rl[Symbol.asyncIterator]();

const readline = async () => (await iter.next()).value;

void async function () {

  let arr=[],time = +(await readline());

  for(let i=0;i<time;i++){

    let line=String(await readline());

    switch(line[0]) {

      case '1':arr.push(line.split(' ')[1]);break;

      case '2':arr.length!=0?arr.shift():console.log('ERR_CANNOT_POP');break;

      case '3':console.log(arr.length!=0?arr[0]:'ERR_CANNOT_QUERY');break;

      default: console.log(arr.length);break;

    }

  }

}()