function c = unique_stable(a)
	[c, ~, ic] = unique(a);
	ia = arrayfun(@(n) find(ic == n)(1), 1:numel(c));
	c = a(sort(ia));
end
function c = unionize_if_intersect(c)
	if numel(c) < 2, return, end
	for ij = nchoosek(1:numel(c), 2)'
		if ~isempty(intersect(c{ij(1)}, c{ij(2)}))
			c{ij(1)} = union(c{ij(1)}, c{ij(2)});
			c(ij(2)) = [];
			c = unionize_if_intersect(c);
			break
		end
	end
end
function c = f(a)
	u = unique_stable(cell2mat(cellfun(@(s) {strsplit(s, "=")}, a)));
	h = @(k) find(strcmp(u, k))(1);
	c = cellfun(@(s) {arrayfun(@(s) h(s), strsplit(s, "="))}, a');
	c = cellfun(@(iu) {u(iu)}, unionize_if_intersect(c));
end
a = {"a1=a2", "b1=b2", "b3=b2", "c1=c2", "e1=e2", ...
     "a3=a4", "c3=c4", "e1=e3", "a2=a4", "c3=c1", ...
     "b3=a4", "c2=d1", "a4=a5", "d2=c1", "b4=b3", "d3=c3"};
disp(['[' strjoin(cellfun(@(s) {['["' strjoin(s, '", "') '"]']}, f(a)), ', ') ']'])

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