how to find out the length of an array?

[jessica1234]

I have a function returning a 2D array which the size dynamically created at runtime.

  int** getArray()

now after i call this function, how do i find out the length of the returned array?

thank you.

[jlb]

You will need to somehow return the array size from the function.

[dhayden]

You can't. That's one of the disadvantages of accessing raw arrays via pointers. Consider returning a vector<vector<int>> instead.

[48T7M4Gy]

Show us how you declare the array please.

[48T7M4Gy]

While it is not as user convenient as using STL containers, particularly vectors, a 2d dynamic array can be organised quite simply to effectively 'know' its size. Once the dimensions are determined, like all c-style array manipulations they must be included in any subsequent function calls. Tedious but nevertheless quite easily done.

// Modified from http://stackoverflow.com/questions/15908632/returning-a-two-dimensional-array-from-a-function-in-c

#include<iostream>

int** createTable(int &, int &);

void deleteTable(int**, int rows);
void printTable(int**, int rows, int);

int main()
{
    int rows = 0;
    int cols = 0;
    
    int** table = createTable(rows, cols);
    
    printTable(table, rows, cols);
    deleteTable(table, rows);
    
    return 0;
}

int** createTable(int &r, int &c)
{
    std::cout << "Enter rows cols:";
    std::cin >> r >> c;
    
    int** table = new int*[r];
    for(int i = 0; i < r; i++) {
        table[i] = new int[c];
        for(int j = 0; j < c; j++)
        {
            table[i][j] = (i+j);
        }// sample set value;
    }
    return table;
}

void deleteTable(int** table, int rows){
    if(table){
        for(int i = 0; i < rows; i++){ if(table[i]){ delete[] table[i]; } }
        delete[] table;
    }
}

void printTable(int** table, int rows, int columns){
    for(int i = 0; i < rows; i++){
        for(int j = 0; j < columns; j++){
            printf("(%d,%d) -> %d\n", i, j, table[i][j]);
        }
    }
}