999. 车的可用捕获量

题目：车的可用捕获量

在一个 8 x 8 的棋盘上，有一个白色车（rook）。也可能有空方块，白色的象（bishop）和黑色的卒（pawn）。它们分别以字符 “R”，“.”，“B” 和 “p” 给出。大写字符表示白棋，小写字符表示黑棋。

车按国际象棋中的规则移动：它选择四个基本方向中的一个（北，东，西和南），然后朝那个方向移动，直到它选择停止、到达棋盘的边缘或移动到同一方格来捕获该方格上颜色相反的卒。另外，车不能与其他友方（白色）象进入同一个方格。

返回车能够在一次移动中捕获到的卒的数量。

示例1:

输入：[[".",".",".",".",".",".",".","."],[".",".",".","p",".",".",".","."],[".",".",".","R",".",".",".","p"],[".",".",".",".",".",".",".","."],[".",".",".",".",".",".",".","."],[".",".",".","p",".",".",".","."],[".",".",".",".",".",".",".","."],[".",".",".",".",".",".",".","."]]
输出：3
解释：
在本例中，车能够捕获所有的卒。

示例2:

输入：[[".",".",".",".",".",".",".","."],[".","p","p","p","p","p",".","."],[".","p","p","B","p","p",".","."],[".","p","B","R","B","p",".","."],[".","p","p","B","p","p",".","."],[".","p","p","p","p","p",".","."],[".",".",".",".",".",".",".","."],[".",".",".",".",".",".",".","."]]
输出：0
解释：
象阻止了车捕获任何卒。

示例3:

输入：[[".",".",".",".",".",".",".","."],[".",".",".","p",".",".",".","."],[".",".",".","p",".",".",".","."],["p","p",".","R",".","p","B","."],[".",".",".",".",".",".",".","."],[".",".",".","B",".",".",".","."],[".",".",".","p",".",".",".","."],[".",".",".",".",".",".",".","."]]
输出：3
解释：
车可以捕获位置 b5，d6 和 f5 的卒。

提示：

• board.length == board[i].length == 8
• board[i][j] 可以是 'R'，'.'，'B' 或 'p'
• 只有一个格子上存在 board[i][j] == 'R'

思路

1. 模拟题，按照题目描述做就好
2. 首先定义一个方向数组，遍历四个方向累计得到结果。

实现

func numRookCaptures(board [][]byte) int {
    var ans int
    dt := [4][2]int{{-1, 0}, {1, 0}, {0, 1}, {0, -1}}

    for row := 0; row < 8; row++ {
        for col := 0; col < 8; col++ {
            if board[row][col] == 'R' {
                for _, d := range dt {
                    ans += _impel(board, row, col, d)
                }
                break
            }
        }
    }

    return ans
}

func _impel(board [][]byte, x, y int, d [2]int) int {
    for {
        x += d[0]
        y += d[1]
        if x < 0 || x >= 8 || y < 0 || y >= 8 {
            break
        }

        if board[x][y] == 'B' {
            return 0
        } else if board[x][y] == 'p' {
            return 1
        }
    }

    return 0
}