C++Advanced-Multidimensional Arrays-Lab-4. Diagonal Difference

#include<iostream>
#include<vector>
#include<cmath>

std::vector<std::vector<int>> readVec2DfromInput(int size) {
    std::vector<std::vector<int>> vec2D(size, std::vector<int>(size));
    for (auto& row : vec2D)
    {
        for (int& number : row)
        {
            std::cin >> number;
        }
    }

    return vec2D;
}

int calculateSumPrimeDiag(const std::vector<std::vector<int>>& vec2D, int size) {
    int sum = 0;
    for (size_t i = 0; i < size; i++)
    {
        for (size_t j = 0; j < size; j++)
        {
            if (j == i)
            {
                sum += vec2D[i][j];
            }
        }
    }

    return sum;
}

int calculateSumSecondDiag(const std::vector<std::vector<int>>& vec2D, int size) {
    int sum = 0;
    int i = 0;
    int j = size - 1;

    while (j >= 0)
    {
        sum += vec2D[i][j];
        i++;
        j--;
    }
    return sum;
}

int main() {
    int size;
    std::cin >> size;
    const std::vector<std::vector<int>> vec2D = readVec2DfromInput(size);
    const int sumPimeDiagonal = calculateSumPrimeDiag(vec2D, size);
    const int sumSecondDiagonal = calculateSumSecondDiag(vec2D, size);
    //std::cout << sumPimeDiagonal << std::endl;
    //std::cout << sumSecondDiagonal << std::endl;
    int diffDiagonals = std::abs(sumPimeDiagonal - sumSecondDiagonal);
    std::cout << diffDiagonals << std::endl;
    return 0;
}