Depth Search

#include <iostream>
#include <cmath>
#include <cstring>
#include <algorithm>
#include <vector>

using namespace std;

int n, m, a, b, cnt, arr[101][101], lamps[101], sum;

void dfs(int v)
{
    cnt++;
    lamps[v] = 1;

    for (int i = 0; i < n; i++)
    {
        if(arr[v][i] && !lamps[i]) dfs(i);
    }
}

int main()
{
    //--------------------------------
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    //--------------------------------

    cin >> n >> m;

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

    dfs(m-1);

    cout << cnt;

    return 0;
}