C++ :: Template To Hold Two Dimensional Arrays - Automatic Indexing

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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C :: Declare Two 1-dimensional Parallel Arrays Of Integers That Will Hold The Information Of Up To 10 People

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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#include <stdio.h>
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[Code].....

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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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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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Aug 14, 2013

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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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#include <iostream>
#include <stdio.h>
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[Code].....

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Apr 8, 2014

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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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Code:
#include <iostream>
using namespace std;
class Atom {
public:
float x, y, z;

[Code] .....

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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);

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[Code] ....

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Code:
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Code:
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[Code] .....

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Code:
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template<typename T1, typename T2>
bool compare(const T1& lhs, const T2& rhs) {

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question is does this will give 30.0 always.?

I am using VS2005.

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[code].....

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Code:
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(and somewhere else)

template <typename T>
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and I'm testing it in this way:

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For example:

The way I do it now:

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The way I want to:

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