I was interviewed by five people one by one throughout the day: three in the morning and two in the afternoon.

For the morning interviews, each person first asked me to introduce myself in English. Then, in Chinese, they asked for details about my resume, including my studies and internship experiences. Following that, they posed one or two IQ puzzles, and then one or two programming questions.

If I passed the first three interviews in the morning (with two or more positive feedbacks), I advanced to the second round of interviews in the afternoon. These were with two managers who are the heads of the group or position I applied for. They inquired more about my interests and career plan, and there were also one or two IQ puzzles.

If I received positive feedback from both of them, it would have been congratulations. Unfortunately, I failed the last interview. That's all.

Give an idea to show how to rearrange the array a1, a2, ..., an, b1, b2, ..., bn into a1, b1, a2, b2, ..., an, bn with O(n) computation time cost and O(1) extra memory cost.