Create FrequentTerms.cpp

Solution to Frequency Counting of Words / Top N words in a document.
 
Given N terms, your task is to find the k most frequent terms from 
given N terms.
 
Input format :
 
First line of input contains N, denoting the number of terms to add.
In each of the next N lines, each contains a term.
Next line contains k, most frequent terms.
 
Output format :
 
Print the k most frequent terms in descending order of their frequency. 
If two terms have same frequency print them in lexicographical order.