Working Together — Solution & Editorial

Back to the Problem

Combined rate is 1/A + 1/B = (A+B)/(AB); the time is the reciprocal. Reduce by the gcd.

Complexity: O(1) or O(log)

Watch out: AB overflows 64 bits at 10⁹ each in C++ — reduce by gcd before multiplying (or use 128-bit).