Combinations
A combination is an unordered collection of unique elements (an ordered collection is called a permutation.). Given the set, S, of all possible unique elements, a combination is a subset of the elements of S. The order of the elements in a combination is not important (i.e., two lists with the same elements in different orders are considered to be the same combination). Addtionally, the elements cannot be repeated in a combination (i.e., every element appears once); this is often referred to as "without replacement/repetition".
Thus, for integers n and r with n ≥ r ≥ 0:
Example:
Solution:
Related Topics: