The Master Theorem is used to determine the time complexity of “Divide and Conquer” algorithms. It solves recurrences of the form:

T(n) = aT(n/b) + f(n)

Where:

• n = size of the problem.
• a = number of sub-problems in the recursion.
• n/b = size of each sub-problem.
• f(n) = cost of the work done outside the recursive calls (like dividing and merging).

In Java, this is used to prove that Merge Sort has a complexity of O(n log n).