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C++ Dynamically Allocated Array; Size set by quantity of user input; Writing to a file;


C++ Dynamically Allocated Array; Size set by quantity of user input; Writing to a file;

By : Patricia Vogler
Date : December 05 2020, 12:24 PM
hope this fix your issue , Most likely, this is what you want to do:
code :


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How do I determine the size of a dynamically allocated structure in Java before writing it to a file?

How do I determine the size of a dynamically allocated structure in Java before writing it to a file?


By : flav
Date : March 29 2020, 07:55 AM
like below fixes the issue Just an idea: write the data to a ByteArrayOutputStream, after that, you should be able to call size() to get the actual length in bytes and call toByteArray() to get the byte buffer, that can be written to a file.
code :
public static void main (String[] args) throws java.lang.Exception {
  ArrayList objects = new ArrayList();
  objects.add("Hello World");
  objects.add(new Double(42.0));
  System.out.println(sizeof(objects));               
}

public static int sizeof(Serializable object) {
  ObjectOutputStream out = null;
  ByteArrayOutputStream baos = null;
  try {
    baos = new ByteArrayOutputStream();
    out = new ObjectOutputStream(baos);
    out.writeObject(object);
  } catch (Exception e) {
    e.printStackTrace();
  } finally {
    if (out != null) {
      try {
        out.close();
      } catch (Exception e) {
        e.printStackTrace();
      }
    }
  }

  return baos != null? baos.size() : -1;
}
Read floating point numbers into a dynamically allocated while increasing the size of the array while reading the file

Read floating point numbers into a dynamically allocated while increasing the size of the array while reading the file


By : marc_snowden
Date : March 29 2020, 07:55 AM
I think the issue was by ths following , Rather than using an array, consider using a std::vector, which automatically resizes. In C++, this is strongly preferred to using a raw array, since it's safer and hides the resource management.
In fact, using a std::vector in conjunction with the stream libraries, it's very easy to read a file of tab-separated floating-point values:
code :
ifstream input("my-file.txt");
vector<float> myValues;

for (float f; input >> f; )
    myValues.push_back(f);
ifstream input("my-file.txt");
vector<float> myValues;

myValues.insert(myValues.begin(),
                istream_iterator<float>(input),
                istream_iterator<float>());
ifstream input("my-file.txt");
vector< vector<float> > myValues;

for (string line; getline(input, line); ) {
    stringstream lineStream(line);

    vector<float> thisLine;

    thisLine.insert(thisLine.begin(),
                    istream_iterator<float>(lineStream),
                    istream_iterator<float>());
    myValues.push_back(thisLine);
}
C - Build dynamically allocated array of pointers to structures filled with input from file

C - Build dynamically allocated array of pointers to structures filled with input from file


By : Benson Wamae III
Date : March 29 2020, 07:55 AM
will help you I can give you some snippets on how to look at this problem.
First - I would avoid using class name for any variable, because in many object-oriented programming languages (including C++) it is a keyword and can't be a name of variable.
code :
typedef struct {
   int DBrecordID; // ID for each entry
   char *lastName;
   char *firstName;
   char studentID[8];
   ...
} DBrecord;
2
Doe John 12345678 senior 3.14159 2015
Carl Boss 32315484 junior 2.71 2013
FILE *filePtr; // Define pointer to file
if((filePtr = fopen("records.txt", "r")) == NULL) // If couldn't open the file
{
   printf("Error: Couldn't open records.txt file.\n"); // Printf error message
   exit(1);  // Exit the program
}
char buffer[100]; // Define the buffer
fgets(buffer, 100 /* size of buffer */, filePtr);
int numOfRecords = atoi(buffer);
DBrecord **recs;
recs = (DBrecord **) malloc(sizeof(DBrecord *) * numOfRecords);
int i;
for(i = 0; i < numOfRecords; i++)
{
   recs[i] = (DBRecord *) malloc(sizeof(DBrecord));
}
recs[0]->lastname /* two possibilities */
*(recs[0]).lastname
int i;
for(i = 0; i < numOfRecords; i++)
{
   // Content of cycle reads one line of a file and parses the values into recs[i]->type...
   /* I give you small advice - you can use fgetc(filePtr); to obtain character by character from the file. As a 'deliminer' character you use space, when you hit newline, then the for cycle continues.
   You know the order of stored values in the file, so it shouldn't be hard for you.
   If you don't get it, let me now in comments */
}
./program < records.txt   // Here the file's name is passed to program on stdin
./program records.txt    // Here the file's name is passed as value in `argv`.
int main(int argc, char *argv[])  // this is important!
{
   // code

   return 0;
}
if(argc != 2)
{
  printf("Number of arguments is invalid\n");
  exit(1); // exit program
}
char filename[50]; // buffer for file's name
scanf("%s", &filename); // reads standard input into 'filename' string until white character appears (new line, blank, tabulator).
Array dynamically allocated by file size is too large

Array dynamically allocated by file size is too large


By : Sean S.
Date : March 29 2020, 07:55 AM
wish helps you Your input files have several lines, each of which has the textual representation of a number. Your file size function however is counting the total number of bytes in the file. These are not the same.
While you can still use the file size to allocate space (you'll just get more than you need), you need to instead check the return value of scanf to see if a number was read. If not, you jump out of the loop.
code :
int index = 0;
while (fscanf(file0, "%i", &numbers[index]) == 1) {
    index++;
}
while (fscanf(file1, "%i", &numbers[index]) == 1) {
    index++;
}
while (fscanf(file2, "%i", &numbers[index]) == 1) {
    index++;
}

for(i = 0; i < index; i++)
{
    fprintf(output, "%i\n", numbers[i]);
}
C I need to use malloc and a dynamically allocated array however I need to print the user input

C I need to use malloc and a dynamically allocated array however I need to print the user input


By : Eyuel Tesfaye
Date : March 29 2020, 07:55 AM
it helps some times issue 1: you are allocating sizeof(double) to store int
issue 2: You are not traversing array to print numbers
code :
int main(void)
{
  int user_input = 0, elements = 0;
  printf("How many int elements will you enter?\n");
  scanf("%d", &elements);

  int* dynamic_array = (int *)malloc(sizeof(int)* elements);
  if(dynamic_array == NULL) {
     perror(" Out of memory ");
     return 0;
  }

  for (int i = 0; i < elements; i++)
  {
    printf("Element %d?\n", i + 1);
    scanf("%d", &dynamic_array[i]);
  }

  for (int printf_number = 0; printf_number < elements; printf_number++)
  {
    printf("Element %d: %d\n", printf_number+1, dynamic_array[printf_number]);
  }

  free(dynamic_array);
  dynamic_array = 0;
  return 0;
}
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