int factorial(int n)

int sum_to_n(int n)

int digit_sum(int n)

int power(int base, int exp)

void descend(int n, void (*on_enter)(int), void (*on_leave)(int))

Print the sequence of moves that solves the Tower of Hanoi for a given disk count

Print all permutations of a unique-character string in lexical order

Print every solution for placing N queens on an N by N board

Print subsets whose values add up to a requested target