Let A be the matrix of numbers. Describe that the minimum number of lines that cover A equals the maximum number of independent non-zero entries of A. (A line is defined to be either a row or a column of A . A set of lines S covers A if each non-zero entry of A is in some line in S . A set of entries T in A is independent if any two different entries in T are located in different rows and in different columns.)
Hint: Use the Konig's theorem on bipartite graphs.