Solution.java

class Solution {
    public int numRookCaptures(char[][] board) {
        final int[] dirs = {-1, 0, 1, 0, -1};
        int n = board.length;
        for (int i = 0; i < n; ++i) {
            for (int j = 0; j < n; ++j) {
                if (board[i][j] == 'R') {
                    int ans = 0;
                    for (int k = 0; k < 4; ++k) {
                        int x = i + dirs[k], y = j + dirs[k + 1];
                        while (x >= 0 && x < n && y >= 0 && y < n && board[x][y] != 'B') {
                            if (board[x][y] == 'p') {
                                ++ans;
                                break;
                            }
                            x += dirs[k];
                            y += dirs[k + 1];
                        }
                    }
                    return ans;
                }
            }
        }
        return 0;
    }
}