Math -> BSGS / Discrete Log

Recover the exponent in a^x ≡ b (mod m) with gcd reduction first and baby-step giant-step second, when square-root storage is still contest-safe.

• Topic slug: math/bsgs-discrete-log
• Tutorial page: Open tutorial
• Ladder page: Open ladder
• Repo problems currently tagged here: 1
• Repo companion pages: 4
• Curated external problems: 2

Microtopics

• discrete-log
• baby-step-giant-step
• meet-in-the-middle
• gcd-reduction
• mod-inverse
• minimum-exponent

Learning Sources

Source	Type
cp-algorithms discrete logarithm	Reference
OI Wiki BSGS	Reference
Library Checker Discrete Logarithm Mod	Practice

Practice Sources

Source	Type
LibreOJ #6542	Practice
Codeforces problemset	Practice

Repo Companion Material

Material	Type
Discrete Log hot sheet	quick reference
Discrete Logarithm Mod	flagship note
Template Library exact starter route	starter route
Chinese Remainder / Linear Congruences	compare point

Curated External Problems

Core

Problem	Source	Difficulty	Context	Style	Prerequisites	Tags	Why it fits
Discrete Logarithm Mod	Library Checker	Hard	Discrete Logarithm	Math; Meet-In-The-Middle; Implementation	Modular Arithmetic; Extended Euclid; Square Root Decomposition	Discrete Log; Meet In The Middle; GCD Reduction	The cleanest verifier for the repo's exact route: general discrete log with gcd reduction and a minimum-answer BSGS implementation.

Stretch

Problem	Source	Difficulty	Context	Style	Prerequisites	Tags	Why it fits
LibreOJ #6542	LibreOJ	Hard	Discrete Logarithm	Math; Implementation	Bsgs; Modular Arithmetic	Template; Discrete Log	A classic template-style benchmark once the first verifier route is already trusted.

Repo Problems

Code	Title	Fit	Difficulty	Pattern	Note	Solution
DISCRETELOGARITHMMOD	Discrete Logarithm Mod	primary	hard	-	Note	Code

Regeneration

python3 scripts/generate_problem_catalog.py