ADD: Implementation of the Euclidean algorithm for finding the greatest common divisor of 2 integers.
ADD: Implementation of the Roy-Floyd algorithm for finding the all-pairs shortest paths in an undirected graph.
FMT: Added comments to the longest common substring implementation.
ADD: Overloaded implementation of longestCommonSubstring to also accept String parameters and return a String.
FMT: Added comments to the longest common substring C++ implementation
Merge branch 'upstream'