Using dynamic multi-dimensional arrays in c++

Question

I am making a C++ program that checks if given aray is a latin square. I need to use a dynamic multi-dimensional array that stores given latin square. But I cant pass the array to a function that does the checking...

Currently I have such code for calling the function:

int squaretest(int **p, int n, int sum) {

    //some code
};

And this code is for creating the array:

int main() { 

    //some code. n - length of one row, sum - sum of elements in one row.
    int a;  
    int **lsquare;
    lsquare = new int*[n];
    for (int i=0;i<=n-1;i++) for (int j=0;j<=n-1;j++) {
        cin >>a;
        lsquare[i][j] = a;
    }
    blocktest(lsquare,n,sum);
    //some code
};

The code compiles (i am using Geany IDE and G++ compiler) but when I run it in terminal, after the first imput, that has to be stored in block[0][0] I get Segmentation fault error. What's wrong with my code and what is the correct sollution?

Answer 1

To be able to do that.. You actually need to do this:

int **lsquare = new int*[n];

for (int i=0; i<n; ++i)
    lquare[i] = new int[n];

for (int i=0; i<n; i++)
    for (int j=0; j<n; j++)
        cin >> lsquare[i][j];

blocktest(lsquare,n,sum);

The better system would be to do:

int *lsquare = new int[n*n];

for (int i=0; i<n; ++i)
    for (int j=0; j<n; ++j)
        cin >> lsquare[i + j*n];

blocktest(lsquare, n, sum);

Answer 2

You forgot to allocate memory for second dimension of the matrix.

int **lsquare;
lsquare = new int*[n];
for (int i=0; i<n; ++i){
  lsquare[i] = new int[n];
....}

nobody writes

for (int i=0;i<=n-1;i++){...}

Do instead

for (int i=0; i<n; ++i){...}