Fast intersection of two sorted integer arrays

Question

I need to find the intersection of two sorted integer arrays and do it very fast.

Right now, I am using the following code:

int i = 0, j = 0;

while (i          


        

Answer 1

Have you tried something simple like this:

var a = Enumerable.Range(1, int.MaxValue/100).ToList();
var b = Enumerable.Range(50, int.MaxValue/100 - 50).ToList();

//var c = a.Intersect(b).ToList();
List c = new List();

var t1 = DateTime.Now;

foreach (var item in a)
{
    if (b.BinarySearch(item) >= 0)
        c.Add(item);
}

var t2 = DateTime.Now;

var tres = t2 - t1;

This piece of code takes 1 array of 21,474,836 elements and the other one with 21,474,786

If I use var c = a.Intersect(b).ToList(); I get an OutOfMemoryException

The result product would be 461,167,507,485,096 iterations using nested foreach

But with this simple code, the intersection occurred in TotalSeconds = 7.3960529 (using one core)

Now I am still not happy, so I am trying to increase the performance by breaking this in parallel, as soon as I finish I will post it