Invariant sets of arcs in network flow problems
Discrete Applied Mathematics
Three-Dimensional Statistical Data Security Problems
SIAM Journal on Computing
Discrete Mathematics
Journal of Combinatorial Theory Series A
On weighted sums in Abelian groups
Discrete Mathematics
Editorial: in memoriam: Alberto Del Lungo (1965-2003)
Theoretical Computer Science - In memoriam: Alberto Del Lungo (1965-2003)
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In this paper, we present a result concerning the reconstruction of permutation matrices from their diagonal sums. The problem of reconstructing a sum of k permutation matrices from its diagonal sums is NP-complete. We prove that a simple variant of this problem in which the permutation matrices lie on a cylinder instead of on a plane can be solved in polynomial time. We give an exact, algebraic characterization of the diagonal sums that correspond to a sum of permutation matrices. Then, we derive an O(kn2)-time algorithm for reconstructing the sum of k permutation matrices of order n from their diagonal sums. We obtain these results by means of a generalization of a classical theorem of Hall on the finite abelian groups.