With regards to the first problem, it is pretty easy if you can have
all the primes precomputed. As a matter of fact, if you search the net,
you'll find the list of all prime no.s that can be stored as a 4 byte
unsigned integer !!. Just use that list of primes to find out the
nearest with the help
What are the limits for the problems ? Are the programming contest problems ?
1.
If not too much .. precompute all primes till the limit and then you
can easily find using binary search the higher and lower primes.
2.Just create a binary tree and see ? Is that too much time ?
Let me know limits
