function getSequence(arr) {
  let maxLength = 0; // 记录最长递增子序列的长度
  let maxSeq = []; // 记录最长递增子序列

  let sequences = new Array(arr.length).fill().map(() => []);

  //   console.log(sequences);

  // 遍历数组
  for (let i = 0; i < arr.length; i++) {
    // 创建一个以当前元素为结尾的递增子序列
    let seq = [arr[i]];
    // 遍历之前的元素，找到比当前元素小的元素，从而构建递增子序列
    for (let j = 0; j < i; j++) {
      if (arr[j] < arr[i]) {
        // 把之前存储的序列和当前元素拼接起来
        seq = sequences[j].concat(arr[i]);
      }
    }

    // 将当前递增子序列存储起来
    sequences[i] = seq;

    // 更新最大的序列
    if (seq.length > maxLength) {
      maxLength = seq.length;
      maxSeq = seq;
    }
  }
  //   console.log(sequences);
  return maxSeq;
}

const list = [2, 1, 5, 3, 6, 4, 8, 9, 7];
const result = getSequence(list);
console.log(result); // [ 1, 3, 4, 8, 9 ]