Q13机器人的运动范围

机器人运动范围

题目

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？

思路

回溯法

count可以传入也可以累积

//找出下面代码里面的bug!
class Solution {
public:
    int movingCount(int threshold, int rows, int cols)
    {
        if(threshold<0 || rows<=0 || cols<=0)
            return 0;
        
        bool *visit = new bool[rows*cols];
        memset(visit, false, rows*cols);
        
        int count = movingCountCore(threshold, rows, cols, 0, 0, visit);
        
        delete[] visit;
        return count;
    }
    
    int movingCountCore(int threshold, int rows, int cols, int r, int c, bool* visit)
    {
        int count = 0;
        if(r>=0 && r<rows && c>=0 && c<cols && !visit[r*rows+c] 
           && (digitSum(r)+digitSum(c))<=threshold)
        {
            visit[r*rows+c] = true;
            count = 1+movingCountCore(threshold, rows, cols, r+1, c, visit)
                +movingCountCore(threshold, rows, cols, r-1, c, visit)
                +movingCountCore(threshold, rows, cols, r, c+1, visit)
                +movingCountCore(threshold, rows, cols, r, c-1, visit);
        }
        return count;
    }
    
    int digitSum(int num)
    {
        int sum = 0;
        while(num>0)
        {
            sum += num%10;
            num = num/10;
        }
        return sum;
    }
};

//应该是 r*cols+c ，写错成了 r*rows+c

//ok
class Solution {
public:
    int movingCount(int threshold, int rows, int cols)
    {
        if(threshold<0 || rows<1 || cols <1)
            return 0;
        bool *accessible = new bool[rows*cols];
        memset(accessible, 0, rows*cols);
        int count = 0;
        
        movingCountCore(threshold, accessible, rows, cols, 0, 0, count);
        
        delete[] accessible;
        return count;
    }
    
    void movingCountCore(int threshold, bool* accessMatrix,
                        int rows, int cols, int r, int c, 
                        int& count)
    {
        if(checkAccessible(threshold, accessMatrix, rows, cols, r, c))
        {
            count+=1;
            accessMatrix[r*cols+c] = true;
            movingCountCore(threshold, accessMatrix, rows, cols, r+1, c, count);
            movingCountCore(threshold, accessMatrix, rows, cols, r-1, c, count);
            movingCountCore(threshold, accessMatrix, rows, cols, r, c+1, count);
            movingCountCore(threshold, accessMatrix, rows, cols, r, c-1, count);
        }
    }
    
    bool checkAccessible(int threshold, bool* accessMatrix, 
                         int rows, int cols, int r, int c)
    {
        int number = sumOfIntNumber(r) + sumOfIntNumber(c);
        if(r<rows && c<cols && r>-1 && c>-1 && accessMatrix[r*cols+c]==false 
           && number<=threshold)
            return true;
        else
            return false;
    }
    
    int sumOfIntNumber(int num)
    {
        int sum = 0;
        while(num>0)
        {
            int tail = num%10;
            num = num/10;
            sum += tail;
        }
        return sum;
    }
};