I had a .NET C# job interview and one of the questions was "Initialize array of integers with values 1,2,3...100 WITHOUT a loop, without recursion and without initialization such as
int[] arr = new [] {1, 2, 3, ...100};
Is it possible?
3 Answers
One-Liner:
Enumerable.Range(1,100).ToArray();
answered Dec 2, 2016 at 11:12
Manfred Radlwimmer
13.4k13 gold badges55 silver badges65 bronze badges
7 Comments
Matteo Umili
I'm a bit poor in terminology, so forgive me if I'm saying something idiot: is this an initialization or you will do just an assignment?
cokceken
It returns an array you need to assign to your variable
Manfred Radlwimmer
@MatteoUmili Sure, why not? You can of course put
int[] array = in front of it to make it more obvious.
Tim Schmelter
Well, it also uses (two) loops, i wonder if it's allowed for OP
Manfred Radlwimmer
Would be interesting to know what the "expected" answer was.
|
C++ solution (sorry, never been in bed with C#) - side effect of some other operations.
struct foo {
static std::vector<int> bar;
// constructor
foo() {
bar.push_back(bar.size());
}
};
// C++ style of initialization of class/static variables
std::vector<int> foo::bar;
int main() {
do {
foo x[100]; // this initializes the foo::bar, goes out of scope and the memory
// is freed, but the side effects persist
} while(false);
std::cout << foo::bar.size() << std::endl; // yeap, 100
int* myArray=foo::bar.data();
// ^
// +--- use it before I change my mind and do...
foo::bar.clear();
foo y[200];
}
3 Comments
Matteo Umili
In
C# when you do foo x[100];, the elements are not automatically initialized with the default constructor, so you'll have an array with 100 null elements. (and no side effect). Still +1 because I like the idea
Adrian Colomitchi
@MatteoUmili Not even when you allocate structs (values) and not references? I don't know enough C#, but what I'm reading says otherwise. (yes, I know, the trick won't work as it is for Java, where all objects are 'by reference')
Matteo Umili
In C#
Structs cannot contain explicit parameterless constructors (CS0568)C# solution - not a cycle, no recursion, not initialization as such, a great method to take a break... uses event queuing provided by the framework/OS - of course one will never use something like this in practice but it is obeying the requirements to the letter (I'll talk about the spirit juuust a bit later). Also, may be ported on many languages, javascript included (see setinterval).
Now, excuse me for a moment, I need to uninstall Mono (and take a shot or two of some strong spirit to get over the trauma):
using System;
using System.Timers;
using System.Threading;
namespace foo
{
class MainClass
{
public static void Main (string[] args)
{
int[] a=new int[100];
a [99] = 0;
int count = 0;
System.Timers.Timer tmr = new System.Timers.Timer();
tmr.Interval = 36000; // so that we can have a beer by the time we have our array
tmr.Elapsed += async ( sender, e ) =>
{ if(count<a.Length) a[count]=count++; }
;
tmr.Start ();
while (a [99] < 99) {
Thread.Sleep (10);
}
foreach(int i in a) {
Console.WriteLine (i);
}
}
}
}
2 Comments
Cody Gray
If you wrote this in an interview, and you got hired instead of laughed out of the room, the company is not one that you want to work for. There would not be enough spirits in the world to get you through your initial browsing of the code base.
Adrian Colomitchi
@CodyGray "the company is not one that you want to work for" this simple OP question is an enough sign I wouldn't like to work for them. To a stupid question, a stupid answer is the best answer.
int arr[] = new int[100];arr[0]=1;arr[1]=2;arr[2]=3.....int[] notTheArrayYouWantMeToInitialize = new[] {1,2,3...100}; int[] definitelyTheArrayYouWantMeToInitialize = notTheArrayYouWantMeToInitialize;