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Cannot apply indexing with [] to an expression of type "int"

Cannot apply indexing with [] to an expression of type "int"

Quang Dinh Luong

Quang Dinh Luong

11y7.5kC# Corner

int n = int.Parse(textBox2.Text);

int Primes[n + 1];

for (int i = 0; i <= Sqrt(n); i++)

Primes[i] = 1;

Primes[0] = 0;

Primes[1] = 0;

for(int i = 2; i <= n; i++)

{

if(Primes[i] == 1)

{

for (int j = 2; i * j <= n; j++)

Primes[i * j] = 0;

}

}

The error is the subject!

I marked error code as red!

Is anyone know why?

Thanks

5 Replies

Know the answer? Post it — somebody with the same question will find it here.

Sujeet Suman11y ago
Accepted answer
Quang please once try below code. I have coloured correction in green colour.

int n = int.Parse(textBox1.Text);
int[] Primes = new int[n+1];
for(int i = 0; i <= System.Math.Sqrt(n); i++)
         Primes[i] = 1;
Primes[0] = 0;
Primes[1] = 0;
for(int i = 2; i <= n; i++)
{
      if(Primes[i] == 1)
      {
         for(int j = 2; i * j <= n; j++)
                  Primes[i * j] = 0;
      }
}

If this is helpful for you then please accept my Answer.
Priyaranjan K S11y ago
Happy to help . Cheers :)
Sujeet Suman11y ago
Your most welcome Quang. We are friends here to help each other. Accepting answer is your appreciation only.
Quang Dinh Luong11y ago
Thanks both! You guys great!!!
I marked Sujeet as the correct answer because the answer is easy to understand
Thanks again Priya and Sujeet! :)
Priyaranjan K S11y ago
Hi,

Try this out . It should work now .

int n = int.Parse("5");
int[] Primes;
Primes = new int[n+1];
for (int i = 0; i <= Math.Sqrt(n); i++)
Primes[i] = 1;
Primes[0] = 0;
Primes[1] = 0;
for(int i = 2; i <= n; i++)
{
if(Primes[i] == 1)
{
for (int j = 2; i * j <= n; j++)
Primes[i * j] = 0;
}
}

This is the proper syntax for array declaration :
int[] numbers; // declare numbers as an int array of any size
numbers = new int[10]; // numbers is a 10-element array

Thanks,
Priyan

If you found this useful Please mark this as Answer