DFS / BFS

#include <iostream>

    using namespace std;

int a[20][20],n, b[20],c[20], st = 0, dr = 0;

int main()

{

    cin >> n >> c[0]; b[c[0]] = 1;

    for (int i = 1; i <= n; i++)

        for (int j = 1; j <= n; j++) cin >> a[i][j];

    while (st <= dr)

    {

        int x = c[st];

        for (int i = 1; i <= n; i++) 

            if (a[x][i]  && !b[i])  { dr++; c[dr] = i; b[i] = 1;}

        for (int i = st; i <= dr; i++) cout << c[i] <<" ";

        cout << endl;

        st++;

    }

    return 0;

}