DFS on Grid

#include<bits/stdc++.h>
using namespace std;

#define loop(i, n)          for(int i = 0; i < n; i++)

///----------------------graph moves----------------*/
int dr[] = {+1, -1, +0, +0};
int dc[] = {+0, +0, +1, -1};

const int N = 100;
int n;
int grid[N][N];
int vis[N][N];

void dfs(int r, int c){
    vis[r][c] = 1;
    loop(k, 4){
        int vr = r + dr[k];
        int vc = c + dc[k];
        if(vr == n or vr < 0 or vc == n or vc < 0) continue;
        if(!vis[vr][vc]) dfs(vr, vc);
    }
}

int main()
{
    #ifndef ONLINE_JUDGE
   // read();
    #endif // ONLINE_JUDGE
   //fastIO;
   int n;
   cin >> n;

   dfs(0, 0);


}