find if two arrays contain the same set of integers without extra space and faster than NlogN

Question

I came across this post, which reports the following interview question:

Given two arrays of numbers, find if each of the two arrays have the same s

Answer 1

I'm not sure that correctly understood the problem, but if you are interested in integers that are in both array:

If N >>>>> 2^SizeOf(int) (count of bit for integer (16, 32, 64)) there is one solution:

a = Array(N); //length(a) = N;
b = Array(M); //length(b) = M; 
//x86-64. Integer consist of 64 bits.

for i := 0 to 2^64 / 64 - 1 do  //very big, but CONST
  for k := 0 to M - 1 do
    if a[i] = b[l] then doSomething;   //detected

for i := 2^64 / 64 to N - 1 do
 if not isSetBit(a[i div 64], i mod 64) then
   setBit(a[i div 64], i mod 64);

for i := 0 to M - 1 do
 if isSetBit(a[b[i] div 64], b[i] mod 64) then doSomething; //detected

O(N), with out aditional structures