可以被一步捕获的棋子数

// Solution using Java Streams
// In this solution, we'll use the Stream API to simulate the movements
// of the Rook in all four directions. However, note that streams in Java
// are typically not used for this type of grid traversal due to their
// stateless nature and the imperative nature of the task.
// Here, we're illustrating how to use streams but it's not the best use case.

import java.util.stream.IntStream;

public class RookCaptureStream {
    public int numRookCaptures(char[][] board) {
        int[] rookPos = findRook(board);
        return IntStream.of(
            countCaptures(board, rookPos, -1, 0), // Up
            countCaptures(board, rookPos, 1, 0), // Down
            countCaptures(board, rookPos, 0, -1), // Left
            countCaptures(board, rookPos, 0, 1) // Right
        ).sum();
    }

    private int[] findRook(char[][] board) {
        for (int i = 0; i < 8; i++) {
            for (int j = 0; j < 8; j++) {
                if (board[i][j] == 'R') {
                    return new int[]{i, j};
                }
            }
        }
        return null;
    }

    private int countCaptures(char[][] board, int[] rookPos, int rowDir, int colDir) {
        int x = rookPos[0], y = rookPos[1];
        while (true) {
            x += rowDir;
            y += colDir;
            if (x < 0 || x >= 8 || y < 0 || y >= 8 || board[x][y] == 'B') break;
            if (board[x][y] == 'p') return 1;
        }
        return 0;
    }
}