core practice · coding problem
GCD and modulo arithmetic
gcd(48,18)? What is (7^10) mod 13 via repeated squaring?
The mechanism
Interviews use math sparingly: gcd/lcm, modular arithmetic, primes, combinatorics, and basic geometry (cross product, line intersection). Recognize the shape of the problem — the formula is a quick lookup away.
Expected evidence
gcd=6; 7^10 mod 13 = 4.
Try this drill in the practice workspace →
Hints when you need them
- Euclidean gcd.
- Binary exponentiation reduces mod each step.