如何從一系列相同的元素只保留上部元素，並刪除其他

Question

下面的表格：

A = [ -1 1 -1 1 -1 1 0 0 0 0 -1 1 0 0 -1 1 -1 1 0 0 ] 

會是這樣的：

A = [ -1 1   0 0 0 0 -1 1 0 0 -1 1  0 0 ] 

Answer 1

有趣的小問題。我相信這個作品：

A = [-1 1 -1 1 -1 1 0 0 0 0 -1 1 0 0 -1 1 -1 1 0 0]; %# Set up an example vector 
I1 = [1, 1, A(1:end-2) - A(3:end)]; %# Index all repetitions of sets of two using zeros 
I1(A == 0) = 1; %# Ensure our index doesn't remove any of the 0's from the original vector 
Soln = A(I1 ~= 0); %# Obtain solution using nonzero entries of the index