The STL provides an algorithm called next_permutation that takes in a range of elements,
then rearranges them to the next lexicographically higher permutation.  For example,
1 2 3 4 becomes 1 2 4 3, or 3 4 2 1 becomes 4 1 2 3.

Write a function NextPermutation that takes in an STL vector<int> and produces the next
permutation of the sequence.  Your function should return true if a next permutation
was available and false otherwise.  That way, you can visit all permutations by writing

do {
     ... process current permutation ...
} while (NextPermutation(myVector));