Leetcode 2010. The Number of Seniors and Juniors to Join the Company II

Count the number of ways to label candidates as seniors or juniors that satisfy a set of pairwise constraints (e.g., relative seniority/preferences or inequality relations). The problem requires modeling constraints as a directed/constraint graph and using graph condensation/topological ordering plus dynamic programming and combinatorics (often with modular arithmetic) to count valid assignments efficiently.