C++ :: How Single Dimensional Arrays Are Stored On The Heap
Aug 14, 2013
I've got a VERY experimental function which takes data stored to a file and assigns it to a multidimensional array on the heap. It's designed for infinite dimensions by recalling itself with updated information but I don't think this is very safe.
The template function creates a heap array using a TYPE**, and recalls itself to create the new dimensions. I want to replace this with the much safer method of assigning just a single heap memory array and then only assign using the recalling method (unless I can find anything else).
To do this though I need to know how single dimensional arrays are stored on the heap, as well as multi-dimensional (for n dimensions). Where I can find this information?
btw I only need this for the Windows operating system, 32bit, I'm not exactly sure what 'C++ style' this is but I'm using Microsoft's Visual Studio Express 2012 as my IDE, so whatever that uses.
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Jan 29, 2012
I know that memory addresses in the stack can contain either values or references to other memory addresses, but do these memory addresses also contain methods or are the methods themselves located in the heap?
The confusion comes from the fact that in C# a delegate variable can be assigned either a method's identifier, an inline function, a lambda expression, or a new instance of the delegate type with the method's identifier passed as an argument to the constructor. My guess is that assigning the method's identifier directly to the delegate variable is just a simplified way of calling the delegate type's constructor with the method's identifier as an argument to the parameter, something that the compiler handles for you.
But even in this last case, the delegate variable is said to point toward the method itself. In that case, does it mean that methods are stored in the heap, just as reference type values are?
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Feb 21, 2015
I have started using code::blocks for practicing ,(was using bloodshed dev C++ til now). The thing is that m not able to compile multiple programs stored under a single project , as i have created project by the name of a topic and have decided to solve all problems related to that topic under that project.
When there was only one .cpp file in the project it compiled successfully ,but as soon as i created a second file and compiled it it says "main can be declared only once"
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Jul 31, 2013
How can I concatenate two 2-dimensional int arrays into one larger 3-dimensional array. This question is also valid for the 3-dimensional vectors. I know the command for the one dimensional vector as:
std::vector<int> results;
results.reserve(arr1.size() + arr2.size());
results.insert(results.end(), arr1.begin(), arr1.end());
results.insert(results.end(), arr2.begin(), arr2.end());
and for the one dimensional array as:
int * result = new int[size1 + size2];
copy(arr1, arr1 + size1, result);
copy(arr2, arr2 + size2, result + size1);
But I do not know how to make a 3-dimensional array or vector.
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Jun 14, 2013
i'm trying to write a calculator. the user will enter the terms and they will be stored in arrays. i will be storing those terms in string arrays and then later turn them to double to work with them. but the user should be able to enter terms like sin(252) and the program should be able to recognize it and calculate it.
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Feb 10, 2013
Code:
char str[40][40];
int number = 7;
for (int i=0;i<number;i++){
printf("enter %d th string::",i+1);
scanf("%s",str[i]);
}
Above, I have a little snippet of a code that I'm trying to figure out. I don't really understand how to implement 2d arrays in C that well. But, I mostly want to know is how and where the strings are being stored, especially with the code below.
Code:
for (int i=0;i<number;i++){
printf("enter %d th string::",i+1);
scanf("%s",str[i]);
}
I know that it's asking the user to enter strings, which will be stored into the 2d array. I just don't understand how it's being stored. Will it be placed in the 1st column or 2nd row or something?
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Feb 6, 2013
I have a problem with a pointer and a bidimensional array. Here's the code:
typedef char t_board[5][4];
int i,j;
t_board *copy (t_board b) {
t_board *ptr;
ptr = (t_board *) malloc (sizeof(t_board));
[Code] ...
After this, I print new_board, and its ok; but the following code after the call to copy, crashes. Don't know why. if I remove the statement new_board = copy(some_board); , the code that follows runs ok.
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Oct 28, 2013
So I started taking a C++ class two weeks ago and we just got to arrays. I am confused on how to pull data from two dimensional arrays. The assignment for this topic reads as follows. Write a program that uses a two-dimensional array to store the highest and lowest temperatures for each month of the year. The program should output the average high, average low, and the highest and lowest temperatures for the year. Your program must consist of the following functions:
a. Function getData: This function reads and stores data in the two dimensional array.
b. Function averageHigh: This function calculates and returns the average high temperature for the year.
c. Function averageLow: This function calculates and returns the average low temperature for the year.
d. Function indexHighTemp: this function returns the index of the highest high temperature in the array.
e. Function indexLowTemp: this function returns the index of the lowest low temperature in the array.
I made the getData function. I do know that i am supposed to more then likely use nested loops on each function to iterate through each column. I have been trying to figure this out. I first saw in my book that the array could be variables so naturally I tryed to make the array loop and increment up the column and row each time a item is stored to make it easier to loop in different functions but then i found out that they have to have a constant value and that doesn't work. Here is the code for index high temp that i have been working on. I honestly feel like i'm over thinking this and its easier then what i'm making it out to be. Here is all of the code.
Code:
#include <iostream>
#include <string>
using namespace std;
void getData(int month);
void averageHigh(int month);
void averageLow(int month);
[Code]...
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Mar 30, 2014
I am having a little trouble finding the minimum value in my two dimensional array. I feel like my code is right, but it could be returning the wrong value. Below is my code, this is just my "minimum" function!
Code:
int minimum( int array[][MAX], int size ) {
int i,j,min;
for( i = 0; i < size; i++ ) {
for( j = 0; j < size; i++ ) {
if( array[i][j] < min ) {
min = array[i][j];
[Code] .....
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Jan 2, 2014
Any way to create a very large 2 dimensional array. I am talking in the order of :
int sl[7000][5000];
I am new to C++. Also is there a better way than arrays to handle such a large amount of integers.
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Feb 15, 2013
i want to make a two-dimensional array that is consisted by objects but i dont want to initialize the objects when i make the array.. i just want to make an array that each of his "cells" has the size of an object.For example,
class Human{
int hm=5;
...
};
and now i want to make a two dimensional array that each "cell" has the size of an Human but not a Human itself.
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Nov 8, 2014
#include <iostream>
#include <cassert>
#include <vector>
using namespace std;
vector<int> flatten(int a[100][200]) {
vector<int> v;
for (int i = 0; i < 100; ++i) {
[Code]...
I made a function for two dimensional arrays with vector, but I don't know how to make the test code for it.
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Mar 24, 2012
I am using 2 ARRAYS OF DIFFERENT SIZES in One 2-Dimensional Vector, and my output is not correct. The arrays are size 4 and size 13.
I want COLUMN 0 to have: 55, 66, 77, 88.
I want COLUMNs 1-12 to have 1,2,3,4,5,6,7,8,9,10,10,10,11 in EACH ROW. It would seem that the 2nd loop for the size 13 array would need to loop 4 times in order to fill 4 rows, however, I'm not sure how to do that. Here is what I have so far in code and output:
#include <iostream>
#include <vector>
using namespace std;
int main() {
int typeArray[4] = {55,66,77,88};
int valArray[13] = {1,2,3,4,5,6,7,8,9,10,10,10,11};
[Code] ....
OUTPUT:
55 0 0 0 0 0 0 0 0 0 0 0 0
1 2 3 4 5 6 7 8 9 10 10 10 11
77 0 0 0 0 0 0 0 0 0 0 0 0
88 0 0 0 0 0 0 0 0 0 0 0 0
How to populate rows correctly?
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Jan 29, 2015
I need to create subfunctions to do basic Matrix mathematics (addition, subtraction, etc.) I need to be able to pass bot of my Matrices to subfunctions. I started with the addition sub function and I cant get the code to run. I keep getting expected primary-expression before ']' token error for line 75.
#include <iostream>
#include <stdio.h>
using namespace std;
[Code].....
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Apr 8, 2014
I am working on the game of fifteen.Yes this is home work. I was wondering if it is possible to save the indexes of an element in a two dim array. I need to find the position of the space in the two dim array save it, find the position of the tile which is passed in as an int and swap the two if they are adjacent. Here is my code
Edit: I can do this by saving i and j in separate int variables but is there a more elegant way of doing this
int board[MAX][MAX];
void init();
void swap(int* lhs, int* rhs);
[Code].....
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Mar 20, 2012
Two Hard-coded Arrays into One 2-Dimensional Vector I have 2 arrays, each of them are hard-coded with integer values. I also have one 2-Dimensional vector and I want to put 1 array into the first column of the vector and the other array into the 2nd column of the vector. The reason is that I want to do math on the 2nd column of the vector only.
I am able to accomplish this with 3 arrays. Two of them are 1-Dimensional and the third array is 2-Dimensional.
I know how to pass ONE Array into ONE vector:
Code:
vector<int> myVector(typeArray, typeArray + 4);
however, when I declare a 2-Dimensional vector:
Code:
vector< vector <int> > myVector(3, vector<int> (2,0))
I am not seeing how to add TWO arrays or how to OUTPUT it to the screen.
Here is my code using DevCPP:
#include <iostream>
#include <vector>
#include <Windows.h>
[Code]...
I don't get any errors, however, I don't know how to output it to the screen to see what it looks like.
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Apr 14, 2013
I receive unexpected outcome in my program. Instead of getting all combinations of 0, 1, 2 (i.e. 000, 001, ..., 222) I get only 000 001 002 010 011 012. The idea of the progarm is to create a crystal lattice. Each atom of the lattice has 3 coordinates (x, y, z). That's why I create class Atom. Then I create 3-dim array of the type derived from class Atom. Now each element of the class will represent an atom.
Code:
#include <iostream>
using namespace std;
class Atom {
public:
float x, y, z;
[Code] .....
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Mar 6, 2015
For the past couple of weeks I have been working on a template to hold two-dimensional arrays. Right now I am puzzling over an indexing question.
There are many places in the template where I would like to use initializer_lists to refer to user-specified row and column ranges, particularly in member function arguments. A typical example would be a member function whose declaration would be along the lines of:
Code:
Array<Type>::some_function(std::initializer_list<int> columns, std::initializer_list<int> rows); which could get called via
Code:
arrayInstance.some_function({3:4}, {5:8});
It would be really nice to be able to use Matlab-style indexing to specify the last column, or the last row, in the Array object -- along the lines of
Code:
arrayInstance.some_function({3:4}, {5:END}); where END takes the value -1, and can be defined in Array, or somewhere else.
The way I have tackled this so far was to write myself an Indices PODS class with two elements to hold start and finish values, and a constructor-from-initializer_list that looks something like this:
Code:
Indices::Indices(std::initializer_list<int> range, int replace_value) {
int const *it = range.begin();
start = (*it == END) ? replace_value : *it ; ++it;
finish = (*it == END) ? replace_value : *it ;
...
}
So the elements of "range" give the values of Indices::start and Indices::finish -- but if either of them are entered as END by the user, they will be replaced by replace_value. (The default value of replace_value is END, so Indices::start and Indices::finish will never change if it is omitted.)
I also defined an Indices::endset(int) function to do the same thing for existing Indices objects:
Code:
Indices::endset(int replace_value) {
if (start == END) start = replace_value;
if (finish == END) finish = replace_value;
} Using Indices::endset, you can code up Array::some_function by modifying the above signature to something like
Code:
Array<Type>::some_function(Indices columns, Indices rows) {
columns.endset(this->M);
rows.endset(this->N);
...
}
This does work, and I've been able to use it in practice. However, it is klutzy. What I would really like to be able to do is have the Indices constructor handle value-replacements in "columns" and "rows", instead of needing to put calls to Indices::endset in every single Array<Type> member function that uses this approach.
The basic problem is that, when Array<Type>::some_function is called, there is no easy way of inserting Array<Type>::M and Array<Type>::N into the optional argument of the Indices constructor when "columns" and "rows" are being built.
The Indices class needs somehow to get access to these, and know which one is being used, M or N. So it needs to have some sort of deeper connection to Array<Type>, but I don't know what that connection should be.
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Nov 7, 2014
I am working on a number of utility functions for two dimensional arrays of integers, or matrices. However I am having a problem with segmentation faults, most likely due to errors in using malloc in functions like copyMatrix.
Code:
matrix_utils.h~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//This function checks if two matrices are equal
int isEqual(int **A, int **B, int n);
//This function returns one row of a matrix
int * getRow(int **A, int i, int n);
//This function returns one column of a matrix
int * getCol(int **A, int j, int n);
[Code] ....
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Jan 9, 2015
I have a firmware application that works well where I display simple text messages on an LCD screen. At the moment, the User Interface is only in English and I have the text strings simply declared as follows:
Code:
static char msg1[] = " Welcome ";
static char msg2[] = " Data Read ";
//etc...
I want to add a variable that can set the language dynamically from an external device, and so I thought I could do the following:
Code:
#define ENG 0
#define FRE 1
#define GER 2
//...
static char msg1[ENG][] = " Welcome ";
static char msg2[ENG][] = " Data Read ";
[Code] .....
writeLCD(msg1[cLang][]); When I try to compile the above I get a compiler error at the "static char msg..." declarations. The error is: "error: array type has incomplete element type"
Is this method valid, but I have a simple syntax problem with the arrray declarations? Or is this method unworkable and I should find a different method?
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Jul 30, 2014
In pseudocode and in C code, declare two 1-dimensional parallel arrays of Integers to store the age and weight of a group of people that will hold the information of up to 10 people. Use a For loop to iterate through the array and input the values. This is the code i have, but my array is showing up as 11 and not 10?
Code:
#include <stdio.h>
int main() {
//Define Variables
float Age_Data[10],Weight_Data[10];
float Age_Input,Weight_Input;
[Code] .....
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Sep 29, 2014
I am trying to concatenate two words from a file together. ex: "joe" "bob" into "joe bob". I have provided my function(s) below. I am somehow obtaining the terminal readout below. I have initialized my memory (I have to use dynamic, dont suggest fixing that). I have set up my char arrays (I HAVE TO USE CHAR ARRAYS (c-style string) DONT SUGGEST STRINGS) I know this is a weird way to do this, but it is academic. I am currently stuck. My file will read in to my tempfName and templName and will concatenate correctly into my tempName, but I am unable to correctly get into my (*playerPtr).name.
/* this is my terminal readout
joe bob
<- nothing is put into (*playerPtr).name, why not?
joe bob joe bob
seg fault*/
/****************************************************************/
//This is here to show my struct/playerInit
[Code]....
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Jan 17, 2014
I had a hard question in my C++ final exam and I'm trying to solve it for the last 3 days. I haven't succeded yet! Here is the question: You have a one-dimensional array A[20]={1,2,3,4,...,20} and B[5][4] you have to assign the A array's elements to the B array but there is an order which is: B[5][4] = { { 12, 9, 11, 10 }, { 14, 7, 13, 8 }, { 16, 5, 15, 6 }, { 18, 3, 17, 4 }, { 20, 1, 19, 2 } } and there is a restriction: you can only use ONE for statement, nothing else!
#include <iostream>
#include <iomanip>
using namespace std;
int main(){
int A[20] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,
16, 17, 18, 19, 20 }; // define A array's elements.
int B[5][4] = { 0 }, k = 1; // define B array and k counter.
[code]....
I can't narrow the statements to one,This program works perfectly but it shouldn't be that long, we need ONLY ONE FOR statement, not two!
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Apr 19, 2013
So I'm going through and trying to do a recursive implementation of a Heap. I keep getting access violations for some reason on my sifts (_siftUp) - even though I'm trying to insert into sub[0] (currSize = 0 in the constructor). I don't think either of my sifts are implemented correctly, are they?
Here's my Heap:
Code:
#ifndef HEAP_H
#define HEAP_H
//**************************************************************************
template<typename TYPE>
[Code].....
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Jun 3, 2012
If I have an array, and want to make a heap tree out of it using make heap and sort heap, how would I do it? I'm struggling because I didn't take any course in data structure.
I tried googling stuff and I got to the following:
Code:
#include <algorithm> // for std::make_heap, std::sort_heap
template <typename Iterator>
void heap_sort(Iterator begin, Iterator end) {
std::make_heap(begin, end);
std::sort_heap(begin, end);
}
The thing is, I don't know what's the "Iterator" doing exactly and what's begin/end, how can I use arrays with the former piece of code?
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Feb 6, 2014
I am creating a class that has a private array on the heap with a constructor that takes the size of the array and initializes it on the heap. Later I have to make a deconstructor delete the space and print out free after.In my code, I was able to heap a private array and make a deconstructor, but I don't know how to take the size of the array and initialize it on the heap. My guess is this:
int* size = new int();
Also when you initialize size on the heap, don't you also have to delete it too? If so, where, in the code, do you do that? Here is my code so far.
Class Student {
private:
int size;
int* array = new int[size];
public:
Student(); // Constructor
~Student(); // Deconstructor
[code]....
How do you make a constructor that takes the size of the array and initializes it on the heap
Student::~Student()
{
delete[] array;
cout << "Free!" << endl;
}
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