Function call cannot be matched to a candidate template definition (of a function to receive 2D array by reference) in C++

Novice here trying a different method to pass array-by-reference in C++.
For C++, geeksforgeeks (under title Template Approach (Reference to Array)) shows a way to pass array by reference in C++ by creating a template. I am trying it because it seems a way to not use pointers and still pass arrays of different sizes on every different function call.

Notice in the following code from geeksforgeeks, a template parameter is specified for the size of the array.

// CPP Program to demonstrate template approach
#include <iostream>
using namespace std;

template <size_t N> void print(int (&a)[N])
{
    for (int e : a) {
        cout << e << endl;
    }
}

// Driver Code
int main()
{
    int a[]{ 1, 2, 3, 4, 5 };
    print(a);
}

I have tried to extend the logic for 2D arrays by making a a template as followed:

template <size_t r, size_t c>
float approach_mean(vector<int>& n, float (&a)[r][c], float m, float d) {
    return 0;
}

class Solution {
public:
    int minimumDeviation(vector<int>& nums) {
        float m = accumulate(nums.begin(), nums.end(), 0) / nums.size();
        float dev = 0, devp = 0;
        long double s = 0;
        float r[2][nums.size()];
        for (int i0 = 0; i0 < nums.size(); ++i0) {
            r[0][i0] = nums.at(i0);
            r[1][i0] = m - nums.at(i0);
            dev = dev + abs(m - nums.at(i0));
        }
        dev = dev / nums.size();
        while (devp < dev) {
            devp = dev;
            dev = approach_mean(nums, r, m, dev);
            break;
        }
        return devp;
    }
    
//     float approach_mean() {
        
//     }
};

Upon running this code, I get an error

Line 21: Char 19: error: no matching function for call to 'approach_mean'
            dev = approach_mean(nums, r, m, dev);
                  ^~~~~~~~~~~~~~~
Line 2: Char 7: note: candidate template ignored: could not match 'float' against 'float'
float approach_mean(vector<int>& n, float (&a)[r][c], float m, float d) {
      ^
1 error generated.

I simply can’t think of ways to solve this error. I understand that it is unable to match the return type for some reason even though they are the same.

The entire logic is a WIP for a solution to Problem 1675 on Leetcode which is about reducing the deviation in an array.

Here is a part of the description of the problem:

You are given an array nums of n positive integers.

You can perform two types of operations on any element of the array any number of times:

If the element is even, divide it by 2.
For example, if the array is [1,2,3,4], then you can do this operation on the last element, and the array will be [1,2,3,2].

If the element is odd, multiply it by 2.
For example, if the array is [1,2,3,4], then you can do this operation on the first element, and the array will be [2,2,3,4].

The deviation of the array is the maximum difference between any two elements in the array.

Return the minimum deviation the array can have after performing some number of operations.

>Solution :

The problem is that float r[2][nums.size()]; is not standard C++ as the size of an array must be a compile time constant.

But as nums.size() is not a constant expression and hence it cannot be used to specify the size of an array and also it cannot be used as a template nontype argument as a template nontype argument must be a compile time constant.

You can verify this by changing nums.size() with some constant expression in float r[2][nums.size()]; and you will find out that the mentioned error is gone.

//-----------------v------>nums.size() replaced with 5
        float r[2][5];

Demo with no compile time error