==

# 5 Build an algorithm that returns a uniform random permutation of numbers 1 to n.

#_ Build an algorithm that returns a uniform random permutation of numbers 1 to n.

# Given a stream of integers build an algorithm that returns a uniform random sample of size k using O(k) memory.
# (Coupon collector’s problem) Suppose a kid wants to collect all the cartoon characters in a kinder surprise series. Given that there are n different characters in total and they are distributed uniformly random
# (Balls and bins problem) m balls are thrown into n bins. Each ball has 1/n probability of falling into each bin. What’s the expected number of empty bins?