Array Inside the Size of Another

Question

So I have a program that needs to increment the value in the first array, in whatever position is set by the second array.

i.e: A user enters the number 5 into an array. The program then goes to that position (5) in the second array and increments it's value by one. So far the code works fine, but I have to use Pointer notation and not Subscript, and am struggling with the correct syntax. Here's the code:

void enter_into_frequency(int *frequency_temp, int *user_numbers_temp)
{
     int i;
     for(i=0; i<NO_OF_NUMS; i++)
     {
          //Frequency array, with position as whatever number the user entered
          frequency_temp[user_numbers_temp[i]]++; //Need this in pointer notation
     }
}

It is always good to know that `a[i]` is equivalent to `*(a + i)` in pointer notation. (for 2D, `a[i][j]` is equivalent to `*(*(a + i) + j)`. Hope that helps. — David C. Rankin, Mar 03 '16 at 09:33

score 3 · Accepted Answer · edited May 23 '17 at 12:15

3

The code you need in pointer notation would be the following:

 ( *(frequency_temp + *(user_numbers_temp + i)) )++;

You can dereference a pointer using the *-operator and if you add an offset to your pointer you are able to dereference your array.

You can also have a look on this What does “dereferencing” a pointer mean?

edited May 23 '17 at 12:15

Community

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answered Mar 03 '16 at 09:05

Frodo

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ameyCU · Answer 2 · 2016-03-03T09:15:13.360

2

( *( frequency_temp + ( *(user_numbers_temp + i) ) ) )++;

This can be used in place of what you have right now.

/*  user_numbers_temp[i]  ->  *(user_numbers_temp+i)    */
/*  frequency_temp[user_numbers_temp[i]]  -> *(frequency_temp+(*(user_numbers_temp+i))) */

And then apply the ++ operator .

edited Mar 03 '16 at 09:15

answered Mar 03 '16 at 09:08

ameyCU

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Array Inside the Size of Another

2 Answers2