Comparing arrays of different sizes without any loop

Question

The question goes like this:

Given two arrays, a & b (both with positive integers).

A special number is a number whi

Answer 1

Well, turns out there might be a way after all :). We make use of the fact that the numbers have to be strictly positive to be special numbers at all.

%# in case we need to handle empty inputs: replace empty input with 0 or 1, respectively.
a = sum(a(:)',1);
bIsEmpty = isempty(b);
b = sum(b(:)',1); b = max(b,1);

specialNumber = find(a==1:length(a));

maxAB = max(max(a), max(b));

%# "zeros()"
bigVectorForComparisonA = (1:maxAB)*0;
bigVectorForComparisonB = (1:maxAB)*0;

bigVectorForComparisonA(specialNumber) = 1;
bigVectorForComparisonB(b) = 1;

%# instead of &, we add. Find only the smallest match
specialNumberInB = find(bigVectorForComparisonA + bigVectorForComparisonB == 2,1,'first');

out = sum(specialNumberInB) * ~bIsEmpty; %# sum([]) = 0

For a slightly prettier solution that assumes up to 1 special number in a

specialNumber = min(find(a==(1:length(a)));

out = any(b==specialNumber)*sum(specialNumber);