Finding consecutive zeros in an array. Not able to solve using diff command

I have an array like below

a=[0 0 1 1 -1 0 0 0 1 1 1 -1 0 0 1 -1] %in my actual code, there are many elements

There is a -1 after every set of 1s like an end marker. I want to find the largest number of consecutive zeros present. Here it would be 3.

I used diff(a) but in this case even 1-1=0 along with 0-0=0. I also tried manipulating the array with some math operations and then using diff(a) but no use.

Any idea on how to do this?

Answer 1

[Stephen23]

a = [0,0,1,1,-1,0,0,0,1,1,1,-1,0,0,1,-1];
d = diff([false,a==0,false]);
b = find(d>0);
e = find(d<0);
m = max(e-b)

m = 3

[Andreia Gomes]

Hello!

How can I do the same, but using a matrix with several rows and columns?

Thank you!

Answer 2

[Matt J]

Using,

https://www.mathworks.com/matlabcentral/fileexchange/78008-tools-for-processing-consecutive-repetitions-in-vectors

[~,~,runLengths]=groupLims(groupTrue(~a),1);

maxLength=max(runLengths)

[Jaya]

This works perfectly fine too. But I accepted the other answer as that code is smaller and I used it.