原创

【剑指Offer】066——机器人的运动范围 (数组)

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?

解题思路

回溯法:从(0,0)开始走,每成功走一步用一个flag数组标记当前位置为1,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。

参考代码

Java

public class Solution {
    public int movingCount(int threshold, int rows, int cols)
    {
        if(threshold == 0)
            return 0;
        int flag[][] = new int[rows][cols]; // 标记
        return count(threshold, rows, cols, 0, 0, flag);
    }
    public int count(int threshold, int rows, int cols, int i, int j, int[][] flag){
        if(i<0 || j<0 || i>=rows || j>=cols || sum(i)+sum(j) > threshold || flag[i][j] == 1){
            return 0;
        }
        flag[i][j] = 1;
        return 1 + count(threshold, rows, cols, i - 1, j, flag) +
                count(threshold, rows, cols, i + 1, j, flag) +
                count(threshold, rows, cols, i, j - 1, flag) +
                count(threshold, rows, cols, i, j + 1, flag);
    }
    public int sum(int i){
        int s = 0;
        while(i>0){
            s += i%10;
            i /= 10;
        }
        return s;
    }
}

Python

# -*- 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)
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