Find the number of islands

Given a grid of size n*m (n is number of rows and m is number of columns grid has) consisting of ‘0’s(Water) and ‘1’s(Land). Find the number of islands.

Note: An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically or diagonally i.e., in all 8 directions.

• Time : O(nm)
• Space : O(nm)

class Solution {
    void bfs(vector<vector<char>>& grid, int sy, int sx, int n, int m) {
        int dy[8]{-1,-1,-1,0,1,1,1,0}, dx[8]{-1,0,1,1,1,0,-1,-1};
        queue<pair<int, int>> q;
        q.push({sy, sx});
        grid[sy][sx] = '0';
        while(!q.empty()) {
            auto p = q.front(); q.pop();
            auto y = p.first, x = p.second;
            for(int i = 0; i < 8; i++) {
                int ny = y + dy[i], nx = x + dx[i];
                if(0 <= ny and ny < n and 0 <= nx and nx < m and grid[ny][nx] == '1') {
                    grid[ny][nx] = '0';
                    q.push({ny,nx});
                }
            }
        }
    }
public:
    // Function to find the number of islands.
    int numIslands(vector<vector<char>>& grid) {
        int n = grid.size(), m = grid[0].size();
        int res = 0;
        for(int i = 0; i < n; i++) {
            for(int j = 0; j < m; j++) {
                if(grid[i][j] == '1') {
                    bfs(grid, i, j, n, m);
                    res++;
                }
            }
        }
        return res;
    }
};