C++ :: Allocating Array Of Pointers To Dynamically Allocated Array?

Jan 18, 2014

I'm trying extremely hard to understand pointers and I have the basic concept down.. I feel as though my knowledge of dynamically allocated pointers and pointers in general is not enough to understand the logic behind what I'm trying to do. The problem is that the donations array must be able to accept any number of donations. I've made it do just that, but there is also an array of pointers which must each point to the same element in the donations array. The program works if I assign int *arrPtr[100] for example, but it does not work if I try to dynamically allocate it to accept the same number of elements for donations entered by the user. Here it's the snippet

#include <iostream>
using namespace std;
//Function Prototypes

[Code]....

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C++ :: Dynamically Allocated Array Of Function Pointers

Dec 13, 2013

I would like to know if this code is correct.

#include <iostream>
#include <string>
int say_one(const std::string &s) {
std::clog << s << ": One!

[Code] .....

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C :: Free Memory From A Dynamically Allocated Array Of Pointers To Linked Lists

Feb 26, 2013

Having some frustrating issues trying to free memory from a dynamically allocated array of pointers to linked lists. I think the problem is in how I initialize the pointers to NULL. Is there a more elegant way to have the program recognize that the list is empty so it knows to create a head node for the linked list in the function 'add_end_stub_to_array'?

I ran the code through Valgrind and it says that memory is definitely lost from this array.

This is the structure definition.

Code: struct stub_edge {
int loc_id;
int anim_type;
int mkt;
struct stub_edge *next_node;
};

Here is the code snippet from main allocating and deallocating memory to the array.

Code:

struct stub_edge **stub_list = (struct stub_edge **)malloc( sizeof(struct stub_edge *) * 12);
for (i = 0; i < 12; i++)
{
stub_list[i] = (struct stub_edge *)malloc(sizeof(struct stub_edge));
stub_list[i] = NULL;
}
stub_list = add_end_stub_to_array(end_stubs, stub_list);
destroy_end_stub_array(stub_list);

Here the function for adding nodes to the lists by reading through a dynamically allocated 2D array. (The end_stubs array is ordered by month and each linked list represents events occuring within the month).

Code:

struct stub_edge **add_end_stub_to_array(int **end_stubs, struct stub_edge **list)
{
long int i = 0;
int mon = 0;
struct stub_edge *current_node1;
struct stub_edge *new_node1;
int break1 = 0;
while(i < num_edges && break1 == 0 && mon < 12)

[Code]...

Here is the function for freeing memory from the list.

Code:

void destroy_end_stub_array(struct stub_edge **list)
{
if(list != NULL)
{
int mon = 0;
struct stub_edge *current_node1;
struct stub_edge *new_node1;
for(mon = 0; mon < 12; mon++)

[Code]...

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C++ :: Dynamically Allocating Multidimensional Array?

Nov 24, 2013

Working on this one from the Jumping into c++ book. The book asks that I create a multidimensional array at run time based on user input and fill it with a multiplication table

My code compiles fine but throws an uninitiated error for p when I try and run it.

Code:
void multiDimentionalMultiplication(int x, int y, int z){
int ***p;
**p = new int[x];
std::cout << "Allocating array.

[code]....

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C++ :: Dynamically Allocating One Dimension Of 3D Array?

Jun 14, 2013

I am trying to figure out the syntax to dynamically allocate a single dimension of a triple dimensional array. Basically i have a 2D array of structs. but each struct is an array (basically rows of the information). The rows of this structure need to be allocated dynamically, but the height and width of the overarching structure are static.

Basically: Struct * ts_FieldInfo[100][100] = new Struct[Class.returndataitems()];

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C/C++ :: Dynamically Allocating Pointer Array

Apr 15, 2014

so I have this code that dynamically allocates a pointer array increasing and removing elements of the array as its operated on.then it sorts and prints out the array when the user is finished operation on the array. i get this error message when running the program though.

"Unhandled exception at 0x0F474F98 (msvcr110d.dll) in Lab10_VarArray.exe: 0xC0000005: Access violation reading location 0xCCCCCCC0."

this is my code

#include <iostream>
#include <cstdlib>
#include "Header.h"
using std::cout; using std::endl; using std::cin;
int main(void) {
char op='x';

[Code]...

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C :: Segmentation Fault When Dynamically Allocating 2D Array

Apr 20, 2013

This is a homework assignment where I have to read a file into a dynamically allocated 2d array. The file format is
10
Jim 3.6
Jake 4.0
Will 3.0
Sara 3.4
Mike 2.5
Ellen 2.9
Melissa 3.9
Eric 3.8
John 3.5
Beth 3.9

where 10 is the number of students followed by the students and the gpa's. There is more to the program but I have not implemented it yet because I am getting a segmentation fault. The output I am getting when I print the array is
Jim 3.6
Jake 4.0
Will 3.0
Sara 3.4
Segmentation fault

I can see where the problem lies. If I raise value for row when I am allocating the rows of the array, all of the names print. I just do not see why I need to. From my understanding the row * sizeof(char*) should give me enough room for 10 entrie.

Code:
#include <stdio.h>
#include <stdlib.h>
void sort();
int main()

[Code] .....

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C/C++ :: Dynamically Allocating Array Passed As Parameter

Apr 18, 2015

I'm trying to dynamically allocate a standard array at runtime in the function of a class where the array is "owned" by the calling class. The calling class knows nothing about the array before it makes the call to create the array other than the datatype of the array. But the full array of data needs to be returned.

It appears that the pointer being passed makes a copy of the pointer on the stack and then when the function returns it pops it off the stack and the array is a memory leak because the pointer is once again a nullptr as it was before being passed and the array has not been deallocated with delete yet (as it should not have been).

(Edit:Unexpected value of MyArray being a nullptr instead of pointing to an array after returning from line 09.)

class Class1 {
void FunctionA() {
Class2 OwnedClass;
int* MyArray = nullptr;
int SizeOfMyArray = 0;

[Code] ....

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C++ :: Dynamically Allocated Array Parameters?

Oct 4, 2014

I have changed my const global int NUMLABS to a non constant variable so that the user can decide how many labs to input. I adjusted the parameters of each function to add NUMLABS becuase the variable is no longer constant. But now main() returns 0 right after the user chooses how many stations to put in each lab. I am having difficulty understanding these dynamically allocated arrays.

/*********************************************************************
Lab4.cpp

This program uses dynamic arrays to store login information for four labs. Each of the four labs is referenced by the labs[] array which is indexed from 0-3. A pointer in the labs[] array then references a dynamic array that is of size for however many computers are in that lab.

Written by: Luca Del Signore
Last modified on: October 3rd
Known bugs: N/A
*********************************************************************/
#include <iostream>
#include <cstdlib>
using namespace std;

[Code]....

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C :: Initialize Dynamically Allocated Array Of Integers To Zero?

Jun 22, 2013

Suppose I wished to initialize a dynamically allocated array of integers to zero. Would I do better to use calloc() or malloc + iterate over all entries setting each to zero? Which one is regarded as a better approach?

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C :: Reallocate A Dynamically Allocated Array Of Structs

Jul 15, 2013

Code:

void readFile(struct course *d, char* filename){
FILE* fp;
char buffer[100];
int i = 0, array_size = 100;
struct course *temp;

[code]....

I will be using this to read data from a file. I start with an array of 100 structures being passed to the readfile function. Once it reads 100 lines (i == array_size), I want to double the array size until I have finished reading the file.

Two questions.

1)My initial thought was that I needed to keep track of the lines read with my variable, i. However, is there a better way?

2)My program is crashing right now at the call to double_array_size function. What is wrong with my code? Never dealt with dynamically allocated array of structures and functions.

I read online that I should change my code in the following manner.

Code:

void readFile(struct course *d, char* filename) {
FILE* fp;
char buffer[100];
int i = 0, array_size = 100;
struct course *temp;

[code]....

I can paste the "error messages" if you like, but it is a page full of stuff I have never seen. glibc detected, Backtrace, Memory Map, and a bunch of numbers and hexadecimal stuff like addresses.

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C :: Storing Array That Is Dynamically Allocated Of A Struct

May 4, 2013

I'm trying to read in a file and store it in an array that is dynamically allocated of a struct (which I'm not sure how to do), then parse each line using strtok() from string.h. The idea is to separate the lines by date, subject, time, etc.

Since the array is a dynamically allocated of typdef struct, it's sorted by the date of each struct, with an intial size of 25. But whenever the array needs to be resized, it should be doubled.

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C :: Can't Input Values In A Dynamically Allocated Array

Oct 5, 2014

this is my function for allocating memory in 2D array

Code:

#include <stdio.h>
#include <stdlib.h>
int allocate_array(int **array, int *row, int *column){
int i;
}

[code]....

end of allocate_array function and this is my function for asking for the values to be stored in array

Code:

int input_array(int **array, int row, int column){
int i, j;
//ask for the values to be stored in the 2D array
for( i = 0; i < row; i++ ){
for( j = 0; j < column; j++ ){
}

[code]....

why I'm having error here in my input_array() function

Code: scanf("%d", &array[i][j]);

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C++ :: Returning Dynamically Allocated 2D Array From Function?

Sep 18, 2014

How can I return a dynamically allocated 2d array from a function? Do I use like this:

int main(){
char **array;
array=func();
} char ** func(){
char** ptr=new char[5]; //five words
ptr[0]=new char[size of word1];
*ptr[0]=word1
........
return ptr;
}

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C++ :: Filling Dynamically Allocated Array With Values

Jan 12, 2013

Just trying to fill a dynamically allocated array with values then I want to print out the values using pointer method:

#include <iostream>
using namespace std;
long * extend_arr(long int arr[], long int length, long int val) {
long * array2 = new long [length + 1];
for (int J = 0; J < length; ++J)
array2[J] = arr[J];

[Code] ....

When this runs, I get an array with random numbers in it. For example, just trying to print the first value in *Block gives me random numbers each time. What is wrong with this as to why it is not holding the right values?

The extend_arr works perfectly fine, because when I try to access the values in the array using indexes (arr[0], arr[1], etc) it shows the right output, but using pointers does not. How can I make it work?

Output:
2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97 134561 23 29 640 112

As you can see, the primes end at 97 but it just keeps printing more

It now prints the correct values in the function if I set the last value in the array to 0. arr[length] = 0;

Now if I wanted to print the values in the array within main, why is that not working?

Nvm, I just changed the void function to return a pointer to an array.

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C++ :: Returning Dynamically Allocated Array From A Function

Jul 27, 2014

This a very simple program I created because I dont understand how do this. My goal is to be able to use the pointer *s5 throughout the program. For example I would to like to call other functions and pass that pointer through the function. I understand the dynamic allocation and pointers for the most part but Im confused here because the "new char[20]" variable will die after the function and I dont want it to.

#include <iostream>
#include <cstdlib>
#include <cstring>
using namespace std;
void testArray ( char *s5 );
int main ( int argc, char *argv[] )

[Code] .....

Also does strlen count the null terminator?

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C++ :: Passing Dynamically Allocated Array In Function?

Feb 13, 2013

In a program I'm working on now, i need a milti-dimensional array. To save space, I used dynamically allocated array by using pointers, something like this-

int *arr;
arr=new int[col*row];

And now i need to pass this array in a function. What are the parameters in the function declaration statement and at the function call statement?

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C/C++ :: Return Pointer To Dynamically Allocated Array

Jun 29, 2014

I'm trying to write a function that returns a pointer to a dynamically allocated array. Here's my code:

#include <iostream>
using namespace std;
void IndexArray(int, int);
int main(){
int *arr, n;

[Code] ....

When I try running the program, I get the error

"Unable to start program 'D:C++FilesdynamicArraySolReleasedynamicArray.exe'. The system cannot find the file specified."

I'm honestly not sure if the issue is my program, or something with C++. At the moment, I cannot debug any of my programs or else I get the same exact error. I basically need to release everything without debugging it. I last used C++ about a year ago and I'm finally back in school, and so trying to get back into it. I use Microsoft Visual C++ 2010.

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C/C++ :: How To Make Two Dimensional Dynamically Allocated Array

Dec 4, 2014

My output becomes nonsense when I changed i value. how can I make tyy[i] value depends both i(depends on cins value) and j(depends on saft.size())

for ( int i = 0 ; i < cins ; i++ ){
for (int j=1 ; j < saft.size() ; j++) {
if (ustk[i] > saft[j] && saft[j-1] > ustk[i]){
tyy[j] = ((ustk[i] - saft[j])*yy[i]);

[code] ....

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C++ :: Create Dynamically Allocated Array And Input Some Information

Feb 25, 2013

I am having some trouble on understanding how to create a dynamically allocated array and then inputting some information in to it from a text file.

Example text file:
John Doe saving 135246978 300 0

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C++ :: Creating / Filling And Deleting Dynamically Allocated Array Of Objects

Jul 26, 2012

Project compile successfully but console turn off with "Windows " with error doesn't print or get anything

Code:
#ifndef Point_HPP // anti multiply including gates
#define Point_HPP
#include <string>
#include <iostream>
#include <sstream>
#include <cmath>

[Code] .....

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C :: Unable To Save A Column Element Into Dynamically Memory Allocated Array

Mar 3, 2014

I am trying to store each value of a column from a text file into an dynamically allocated array, which needs to be globally declared for further usage in the program.The input textfile contains the following:

34932 13854 13854 2012-01-07
172098 49418 53269 2012-01-07

I have written the following code:

Code:

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
int main()
}

[code]....

The commented printf line gives the entire values of the column, which proves that the file is correctly being read.But on compiling this program I get both compiler warnings and finally segmentation fault.

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C/C++ :: Dynamically Creating Array Of Pointers?

Apr 6, 2014

I have a structure, containing a pointer as a member. I dynamically create an array of that structure type, and then need to dynamically create an array for its pointer member.

#include <iostream>
#include <string>
using namespace std;

[Code]....

There is more of my program afterwards, but it shouldn't matter. The errors I am getting at compile time are that I cannot convert an int pointer to an int (line 29) and that test is not a member of CourseGrade (lines 44/45).

My thought is I might be using the * operator incorrectly. My code before hand in line 29 was

for (i = 0; i < numberStudents; i++)
*studentPtr[i]->tests = new int[numberTests];

but the compiler suggested a '.' rather then the '->'

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C++ :: Creating Array Of Pointers To Base Class To Point To Derived Class Objects Dynamically

Jan 16, 2013

Please consider the following code :

#include <iostream>
using namespace std;
class superclass;
class subclass1;
class subclass2;

[Code] ....

As you can see I want to create a dynamically allocated storage of references to a parent class each of which can then point to a child class, how ever I do not know how to extract the child class out again from that array so i may access its variable b.

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C :: Dynamically Allocating Memory?

Sep 18, 2013

I have created a database for music cds:

Code:

#include<stdio.h>
#include<stdlib.h>
#define array
typedef struct cd_database

[Code]....

When I am using malloc instead of arrays the code is not working properly after exit. I have tried alot but can't came up with a way

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C++ :: Dynamically Allocating Hash Table Using Data From File

Nov 5, 2013

I have an abstract based class and three derived classes. I also have a templated hash table class(using chaining as my collision resolution method, an array of stl lists), and a class to parse commands from a file, this also holds the instantiation of the hash table. My question is that since my command parsing class's constructor instantiates the hash table in the main driver(unable to modify) how can I make this dynamically allocated using data from the file?

template<class T>
class hashTable{
public:
hashTable(int size);
~hashTable();

[Code] .....

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