Vectorized method to find the number of consecutive 1s from the left of an array

Hi, I want to find the number of consecutive 1s from the left of an array (a binary array). For example, if I have A = [1 1 1 0 1 0 0 0 1 1] then the result would be 3 because there are 3 consecutive 1s from the left. Another example: A = [1 0 1 1 1 1 1] then the result would be 1. Or A = [0 1 1 1 0 0 1 0 1], the result would be 0.

I can write this in for loop, however I do not know how to vectorize this part. I really need it for my code so that it might run faster.

Please help me, thank you very much.

[Dang Manh Truong]

Perfect! Thank you very much!

[madhan ravi]

[Comment moved to answer section]

[Dang Manh Truong]

Hey, when I try A = [1 1 1 1 1 1] it gives me an error :(

[madhan ravi]

See the edited answer below.

Answer 1

[madhan ravi]

idx=find(diff(A));
if A(1)==0
Result=0
elseif all(A)
Result=numel(A)
else
Result=idx(1)
end