How to initialize a 2D array with all values same?

Question

I want to initialize a 2D array with -1 as all the value. I used memset() for this.

#include 
using namespace std;

int dp[100]         


        

Answer 1

In practice, in this case, it is possible to write an helping templated function, itself based on simple for-range loops.

One advantage is that is will work for other types of 2D arrays.

#include    

template 
void init2d (T2d &arr, T val) {
    for (auto& row: arr) {
        for (auto& i: row) {
            i = val;
        }
    }       
}

int main() {
    const int  n = 5, m = 6;
    int a[n][m];

    init2d (a, -1);
    std::cout << a[n-1][m-1] << "\n";
}

If you want to initialize before main, the simplest way is to rely on STL, e.g. on std::vector or std::array, like this, for a 5x6 matrix:

std::vector> b(5, std::vector (6, -1));