Description: A sparse matrix is a 2D matrix that has many zeros. Assume that for storage efficiency someone has converted a sparse matrix into a compact 2D matrix with dimensions Nx3 where N is the number of non-zero items in the original sparse matrix. In each row of compact, the first column holds the value of a non-zero item of the sparse matrix, the second column holds the row that this item resides in the sparse matrix, and the third column holds the column that this item resides in the sparse matrix. Write a function that given a compact matrix it returns the original sparse matrix. Assume the last row and the last column of the sparse matrix contain at least one non-zero item.