Grid BFS/DFS

#include <iostream>
#include <queue>
#include <utility>
#include <vector>
using namespace std;

const vector<int> dx = {0, 0, 1, -1};
const vector<int> dy = {1, -1, 0, 0};
// const vector<int> dx = {0, 0, 1, -1, 1, 1, -1, -1};
// const vector<int> dy = {1, -1, 0, 0, 1, -1, 1, -1};

bool is_in_bounds(int x, int y, int N, int M) {
  return x >= 0 && x < N && y >= 0 && y < M;
}

void dfs(int x, int y, int N, int M, vector<vector<int>> &grid,
         vector<vector<bool>> &vis) {
  if (vis[x][y]) {
    return;
  }
  vis[x][y] = true;

  for (int i = 0; i < 4; i++) {
    int nx = x + dx[i], ny = y + dy[i];
    if (is_in_bounds(nx, ny, N, M) && !vis[nx][ny] && grid[nx][ny] == 1) {
      dfs(nx, ny, N, M, grid, vis);
    }
  }
}

void bfs(int u, int v, int N, int M, vector<vector<int>> &grid,
         vector<vector<bool>> &vis) {
  queue<pair<int, int>> Q;

  Q.push(make_pair(u, v));
  while(!Q.empty()) {
    pair<int, int> nd = Q.front();
    Q.pop();
    int x = nd.first, y = nd.second;
    vis[x][y] = true;

    for (int i = 0; i < 4; i++) {
      int nx = x + dx[i], ny = y + dy[i];
      if (is_in_bounds(nx, ny, N, M) && !vis[nx][ny] && grid[nx][ny] == 1) {
        vis[nx][ny] = true; // IMPORTANT FOR BFS
        Q.push(make_pair(nx, ny));
      }
    }
  }
}

int main() {
  int N, M; // N x M grid of 0/1
  cin >> N >> M;
  vector<vector<int>> grid(N, vector<int>(M, 0));
  vector<vector<bool>> vis(N, vector<bool>(M, false));
  for (int i = 0; i < N; i++) {
    for (int j = 0; j < M; j++) {
      cin >> grid[i][j];
    }
  }

  int island_count = 0;
  for (int i = 0; i < N; i++) {
    for (int j = 0; j < M; j++) {
      if (!vis[i][j] && grid[i][j] == 1) {
        island_count++;
        dfs(i, j, N, M, grid, vis);
      }
    }
  }

  cout << "Island Count: " << island_count << endl;

  int island_count_bfs = 0;
  for (int i = 0; i < N; i++) {
    for (int j = 0; j < M; j++) {
      if (!vis[i][j] && grid[i][j] == 1) {
        island_count_bfs++;
        bfs(i, j, N, M, grid, vis);
      }
    }
  }

  cout << "Island Count BFS: " << island_count << endl;
}

/*
4 9
0 0 1 0 0 1 1 1 0
0 1 1 1 1 0 1 1 0
0 0 1 1 0 0 1 0 0
0 0 0 0 0 0 0 0 0
 * */