c# strings

x = {1,2,3,4,5,6}
y = {3,4}
z = {6,7}

var x = new HashSet<int>(Enumerable.Range(1,6)); // [1,2,3,4,5,6]
var y = Enumerable.Range(1,3); // [1,2,3]
var z = Enumerable.Range(6,2); // [6,7]
x.IsSupersetOf(y); // true
x.IsSupersetOf(z); // false

if(y[0] <= x[x.length-1])
    //binary search in array x for y[y.length-1]
    //if that is true u can say that y in x else false.