Recognizing balanceable matrices

A 0/ ± 1 matrix is balanced if it does not contain a square submatrix with exactly two nonzero entries per row and per column in which the sum of all entries is 2 modulo 4. A 0/1 matrix is balanceable if its nonzero entries can be signed ±1 so that the resulting matrix is balanced. A signing algorithm due to Camion shows that the problems of recognizing balanced 0/ ± 1 matrices and balanceable 0/1 matrices are equivalent. Conforti, Cornu´ejols, Kapoor andVuˇskovi´c gave an algorithm to test if a 0/±1 matrix is balanced. Truemper has characterized balanceable 0/1 matrices in terms of forbidden submatrices. In this paper we give an algorithm that explicitly finds one of these forbidden submatrices or shows that none exists.

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http://eprints.lse.ac.uk/31723/