Question

I need to implement a very large matrix, say NxN in Standard C. The matrix must store a truth table, that is

matrix[i][j] = [true|false]

I know I could simply use a int matrix, or boolean type if using C99, but was looking for the most lightweight solution in terms of memory.

Answer 1

The most lightweight solution in terms of memory is saving eight boolean in a char:

unsigned char getBit(char byte, unsigned short bit){
    assert(bit < 8);
    return byte&(1<<bit);
}

Then you can store a N x 8M matrix by saving the bytes in each row. If many of those bytes are empty then you should use a sparse matrix format, for example compressed spares row.