Audience and Seat#

13y1.6kVisual Basic .NET

Only one seat should be allocated to one audience randomly. More than one audience can't have same seat or vice versa. How can this program be completed with these conditions?

using System;

class Program
{
public static void Main()
{
int seats = 10;
int audience = 10;

int[] audArray = new int[audience];

Random r = new Random();

Console.WriteLine("{0 ,4} {1, 5}", "Audience", "Seat#");

for (int i = 1; i < audience; i++)
{
int x = r.Next(1, seats);

audArray[i] = i;

Console.WriteLine("{0, 3} {1, 6}", audArray[i], x);

}
Console.Read();
}
}

7 Replies

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Vulpes13y ago
Accepted answer
You need to make sure that a seat hasn't been allocated before. You can do this with the Array.IndexOf method which will return -1 if a seat number isn't already in the array.

So try the following:

using System;

class Program
{
public static void Main()
{
int seats = 10;
int audience = 10;

int[] audArray = new int[audience]; // all elements zero initially

Random r = new Random();

Console.WriteLine("{0 ,4} {1, 5}", "Audience", "Seat#");

for (int i = 0; i < audience; i++)
{
int x = r.Next(1, seats + 1); // random number between 1 and seats

if(Array.IndexOf(audArray, x) == -1) // seat hasn't already been used
{
audArray[i] = x;
Console.WriteLine("{0, 3} {1, 6}", i + 1, audArray[i]);
}
else
{
i--; // need to get another random seat for index i
}
}

Console.Read();
}
}
0
13y ago
Thank you for your explanation.
0
Vulpes13y ago
Before generics was introduced in .NET 2.0, the compiler would have chosen the Array.IndexOf(Array, object) overload.

However, in later versions of .NET, the generic overload Array.IndexOf(T[], T) would be considered the 'best match' for the arguments and would therefore be selected by the compiler.

Incidentally, the compiler uses complex rules to determine the best match but these usually result in the 'common-sense' overload being chosen.

You could still force the Array.Index(Array, object) overload to be chosen by changing the line to:

if(Array.IndexOf(audArray, (object)x) == -1)

but this would be less efficient that the generic alternative as the int would need to be boxed on the heap to be accommodated by the object parameter.

You could also call the generic overload with the syntax:

f(Array.IndexOf(audArray, x) == -1)

but this is unnecessary as the compiler is able to infer the type of T from the types of the arguments.
0
13y ago
I wish to know whether IndexOf(T[], T) was converted into non-generic by removing T and replacing with object and int. That means Array.IndexOf(object, int).
0
Vulpes13y ago
The MSDN docs is as good a place as any:

http://msdn.microsoft.com/en-us/library/eha9t187.aspx

Notice that the overload we're using here is a generic method where T = int. The compiler infers the type of T from the fact that it's an int array and an int value that we're passing to it.
0
13y ago
Is there any website to learn more about Array.IndexOf(object, int) == -1
0
13y ago
Thanks
0