飞地的数量

/*
 * Problem Statement: Find the number of land cells (1s) in the grid that cannot reach the boundary of the grid using Java Streams.
 * Solution Approach:
 * 1. Mark all land cells connected to the boundary as visited using DFS.
 * 2. Use streams to count the number of unvisited land cells.
 */

import java.util.Arrays;

public class Solution {
    public int numEnclaves(int[][] grid) {
        int rows = grid.length;
        int cols = grid[0].length;
        // Mark boundary connected lands
        for (int i = 0; i < rows; i++) {
            if (grid[i][0] == 1) dfs(grid, i, 0);
            if (grid[i][cols - 1] == 1) dfs(grid, i, cols - 1);
        }
        for (int j = 0; j < cols; j++) {
            if (grid[0][j] == 1) dfs(grid, 0, j);
            if (grid[rows - 1][j] == 1) dfs(grid, rows - 1, j);
        }
        // Count the number of enclosed lands using streams
        return Arrays.stream(grid)
                     .flatMapToInt(Arrays::stream)
                     .sum();
    }

    private void dfs(int[][] grid, int i, int j) {
        int rows = grid.length;
        int cols = grid[0].length;
        if (i < 0 || j < 0 || i >= rows || j >= cols || grid[i][j] == 0) return;
        grid[i][j] = 0; // Mark as visited
        dfs(grid, i + 1, j);
        dfs(grid, i - 1, j);
        dfs(grid, i, j + 1);
        dfs(grid, i, j - 1);
    }
}