How can I count the number of 1 after every element of the vector?

I have this vector of 1 and 0:

X= [1 1 1 1 0 0 1 1 0 1 0 1 0 0 1 1]

I want to create a vector Y that counts for every element of X the number of 1 that there are after it (including the 1 of the element, if is 1)

So the vector Y should be:

Y=[4 3 2 1 0 0 2 1 0 1 0 1 0 0 2 1]

How can I do that?

thank you!

Answer 1

[Stephen23]

>> X = [1,1,1,1,0,0,1,1,0,1,0,1,0,0,1,1]
X =
   1   1   1   1   0   0   1   1   0   1   0   1   0   0   1   1
>> Z = cumsum([true,diff(X)>0]);
>> F = @(v){flip(cumsum(flip(v)))};
>> Y = cell2mat(accumarray(Z(:),X(:),[],F)).'
Y =
   4   3   2   1   0   0   2   1   0   1   0   1   0   0   2   1