How do you get this simple DCT flow graph from this simple matrix made up of 1,-1 and 0s?

The matrix above comes from the Discrete Cosine transform (multiplied by 2 and rounded off).
1. Why is it said to have null multiplicative complexity
2. how do you get this signal flow graph below using the matrix above,did i miss something?


am well aware of the fast fourier transform and how some of its principles have been applied here,I just can't figure out how this particular signal flow was determined.

Do not multi-post, one is enough.
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