The first paragraph: In probability theory, the coupon collector's question describes the contest of "collecting all coupons and winning". It answers the following questions: Assuming there are n different coupons, it is also possible to collect coupons and replace them. What are the odds? Is it necessary to collect all n coupons for the inspection of more than t samples? To put it another way: Given that there are n coupons, how many coupons do you expect? Do I need to draw at least once before each coupon is replaced? The mathematical analysis of this problem shows that the expected number of tests is needed ... For example, when n = 50, it takes about 225 to collect all 50 coupons [2].

The key to solving this problem is to understand that it only takes a little time to collect the first few coupons. On the other hand, it takes a long time to collect past coupons. In fact, for 50 coupons, it takes an average of 50 experiments to collect the last coupon, and 49 other coupons have been collected. That's why the expected time to collect all coupons is far beyond 50. The idea now is to take the total time as 50 intervals to calculate the expected time.

I hope you are satisfied with the above translation. If satisfied, still hope to adopt, thank you!