剑指Offer 66. 机器人的运动范围 (回溯)

题目描述

地上有一个m行和n列的方格。一个机器人从坐标0,0的格子开始移动,每一次只能向左,右,上,下四个方向移动一格,但是不能进入行坐标和列坐标的数位之和大于k的格子。 例如,当k为18时,机器人能够进入方格(35,37),因为3+5+3+7 = 18。但是,它不能进入方格(35,38),因为3+5+3+8 = 19。请问该机器人能够达到多少个格子?

题目地址

https://www.nowcoder.com/practice/6e5207314b5241fb83f2329e89fdecc8?tpId=13&tqId=11219&rp=3&ru=/ta/coding-interviews&qru=/ta/coding-interviews/question-ranking

思路

和上一道题十分相似,只不过这次的限制条件变成了坐标位数之和。对于求坐标位数之和,我们单独用一个函数实现,然后套入上一道题的代码中即可。

Python

# -*- coding:utf-8 -*-
class Solution:
def movingCount(self, threshold, rows, cols):
# write code here
if rows < 1 or cols < 1:
return False
visited = [False] * int(rows*cols)
count = self.movingCountCore(threshold, rows, cols, 0, 0, visited)
return count def movingCountCore(self, threshold, rows, cols, row, col, visited):
count = 0
if 0 <= row < rows and 0 <= col < cols and self.getDigitSum(row)+self.getDigitSum(col)<=threshold and not visited[row*cols+col]:
visited[row * cols + col] = True
count = 1+ self.movingCountCore(threshold, rows, cols, row+1, col, visited) + \
self.movingCountCore(threshold, rows, cols, row-1, col, visited) + \
self.movingCountCore(threshold, rows, cols, row, col+1, visited) + \
self.movingCountCore(threshold, rows, cols, row, col-1, visited)
return count
def getDigitSum(self,num):
sum = 0
while num:
sum += num%10
num /= 10
return sum if __name__ == '__main__':
result = Solution().movingCount(18,3,4)
print(result)
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