剑指Offer66：机器人的运动范围

思路：

1.从(0,0)开始走，每成功走一步标记当前位置为true,然后从当前位置往四个方向探索，

返回1 + 4 个方向的探索值之和。

2.探索时，判断当前节点是否可达的标准为：

1）当前节点满足limit限制。

2）当前节点在矩阵内；

3）当前节点未被访问过；

# -*- coding:utf-8 -*-
class Solution:
     
    def __init__(self):
        self.vis = {}
         
    def movingCount(self, threshold, rows, cols):
        # write code here
        return self.moving(threshold, rows, cols, 0, 0)
         
    def moving(self, threshold, rows, cols, row, col):
        if row/10 + row%10 + col/10 + col%10 > threshold:
            return 0
        if row >= rows or col >= cols or row < 0 or col < 0:
            return 0
        if (row, col) in self.vis:
            return 0
        self.vis[(row, col)] = 1
         
        return 1 + self.moving(threshold, rows, cols, row-1, col) + self.moving(threshold, rows, cols, row+1, col) + self.moving(threshold, rows, cols, row, col-1) + self.moving(threshold, rows, cols, row, col+1)