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Reading floats into an array

How could I read let say say 10 floats and store them in an array without wasting any memory?

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6 answers 


int size = 10;
float vet[size];
   for(i = 0; i < size; i++){
      scanf("%f", &vet[i]);
   }


As far as possible :)

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Yeah. It's not reading floats, that's the problem, it's memory. You are reading into i and you want an array that has exactly i floats.

It really smells like homework, which is good, but I'm too much of a teacher to give you a complete answer. So I'll tell you that you need a C function called malloc () and a C operator (it's like a function, but actually built into the language) called sizeof.

Check out this tutorial .

Yes, you are there. Here is the code from your comment, formatted.

int n,index;
float temp;
scanf("%d",&n);
float *pValues=(float *)calloc(n,sizeof(float));
for(index=0;index<n;index++) {
    scanf("%f",&temp); 
    *(pValues+index)=temp;
}

I would do it with two changes:



  • More idiomatic to use malloc

    for anything other than symbols
  • In C, arrays and pointers are very closely related; is actually *(pValues+index)

    exactly equivalent pValues[index]

    .

So, I would rewrite this as:

int n,index;
float temp;
scanf("%d",&n);
float *pValues=(float *)malloc(n*sizeof(float));
for(index=0;index<n;index++) {
    scanf("%f",&temp); 
    pValues[index]=temp;
}

Let's take a look at another code transformation. You have pValues

which is a pointer to float

. You have &temp

, which is also a pointer to float

because it &

is an operator-address, and temp

is float

. And, you're just doing index-index arithmetic. So, we could rewrite this again as:

int n,index;    // Don't need temp
scanf("%d",&n);
float *pValues=(float *)malloc(n*sizeof(float));
for(index=0;index<n;index++) {
    scanf("%f",pValues+index); 
}

Now a quiz question: what happens if you did a loop

for(index=0;index<n;index++) {
    scanf("%f",pValues++); 
}
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You should be more specific about this problem.

If you have anything else you need to do with these numbers, then the easiest way to save memory is to not store them in an array to start with.

It sounds like you want something like.

sum = 0;
make
  read current
  sum + = current
while (you haven't read 10 numbers yet);

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The answer to your question is that you cannot add things to an array and expect the array to use any memory.

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float arr[10];
for(i = 0; i < 10; i++){
    scanf("%f", &arr[i]);
}

I know it is as above, but does not use an extra int in case it is not optimized. hehe

To use even less memory use the code below. They are all read into an array, but only the last one to be read is in the array:

float arr[1];
for(i = 0; i < 10; i++){
    scanf("%f", &arr[0]);
}
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sounds like homework.

read the number of floats from the entrance. multiply by the size of the individual float allocate the exact number of bytes storing the address in the pointer to floats have a loop readable in the floats from the input there is a loop that sums all the floats in the array

My guess is that the lesson lesson is to implement the link between the pointer and the term array, although you can do this without indexing the array, but your question implies that you need to use an array.

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