Random commentary about C++, STL, Boost, Perl, Python, Algorithms, Problem Solving and Web Search
The question of P( s[k]==k for some k) surprisingly comes up all the time in hash tables and sorting. It's a surprising result to most people that the probability converges to a nice value (1-1/e) and doesn't depend much on the size of the population. It's sort of like the Birthday paradox in its "really!??" counter-intuitiveness.