UVa 10789 - Prime Frequency

10789 - Prime Frequency

 * http://acm.uva.es/p/v107/10789.html

Summary
Given a string find the characters a-z A-Z 1-9 that have a prime frequency in the string

Explanation
Generate a mapping of the ascii characters to their frequency. Use precomputed primes to figure out whether the frequency of the ascii character is a prime

Input
3 ABCC AABBBBDDDDD ABCC ABCDFFFF

Output
Case 1: C Case 2: AD case 3: C Case 4: empty