MATLAB: How to set all elements in a 2D Matrix between two indices to “1” in each row

Question

I've a matrix A e.g. like this:

A =

     1     0     0     1     0     0
     0     0     1     0     0     1
     0     1     1     0     0     0
     0     1     0     1     0     0

And I want all elements between the "ones" per row to be "one" as well. The result should look like this: B =

     1     1     1     1     0     0
     0     0     1     1     1     1
     0     1     1     0     0     0
     0     1     1     1     0     0

If it helps, I also have two vectors with the indices of the first and second one.

Thanks!!

PS: If possible the solution would not use any loops since the real matrix that I have to use is very large and the program shall be very efficient.

Answer 1

 cumsum(A,2)==1|A;