How many people are needed at a party such that there is a reasonable chance that at least
two people have the same birthday?
By birthday we mean any of the 365 days of the year.
Our intuition might lead us to assume that we need around 183 people
(i.e., about half the number of days in a year) for a collision to occur.
However, it turns out that we need far fewer people.
$ g++ -o birthday birthday.c++
$ ./birthday