题解 | #数据分类处理#

let firStr;
while ((firStr = readline())) {
  let secStr = readline();
  let I = firStr.split(" ").splice(1);
  let R = secStr.split(" ").splice(1);
  let sortedR = Array.from(new Set(R.sort((a, b) => +a - +b)));
  // [0, 3, 6]
  let result = {};
  sortedR.forEach((item) => {
    let obj = {};
    I.forEach((v, i) => {
      if (v.includes(item)) {
        obj[i] = v;
      }
    });
    if (Object.keys(obj).length) { 
      result[item] = obj;
    }
  });

  let str = "";
  Object.keys(result).forEach((v) => {
    str = `${str} ${v} ${Object.keys(result[v]).length}`
    Object.keys(result[v]).forEach(el => {
      str = `${str} ${el} ${result[v][el]}`
    })
  });
  print(`${str.split(" ").length - 1}${str}`)
}