Sudoku S-permutation matrices and bipartite graphs

The book examines some combinatorial problems related to the number of Sudoku matrices. The problem is reduced to the task of finding the number of mutually disjoint pairs of S-permutation matrices. We describe some algorithms that solve this problem. Essential role in the description of the corresponding formulas and algorithms play bipartite graphs and operations with binary matrices. Solving the main problem we have discussed also other mathematical and algorithmic problems which in itself are interesting.