骑士的可能动作

给定一个尺寸为 m * n 的棋盘。查找可以在棋盘上从给定位置移动骑士的可能移动次数。如果 mat[i][j] = 1 则该块被其他东西填充，否则为空。假设棋盘由所有相同颜色的棋子组成，即没有被攻击的块。

例子：

Input : mat[][] = {{1, 0, 1, 0},
                   {0, 1, 1, 1},
                   {1, 1, 0, 1},
                   {0, 1, 1, 1}}
        pos = (2, 2)
Output : 4
Knight can moved from (2, 2) to (0, 1), (0, 3), 
(1, 0) ans (3, 0).

我们可以观察到棋盘上的马移动：
1.两横一竖
2. 两纵一横
这个想法是存储骑士的所有可能动作，然后计算有效动作的数量。如果出现以下情况，移动将无效：
1.一个块已经被另一个块占用。
2. 走棋出棋盘。

C++

// CPP program to find number of possible moves of knight
#include 
#define n 4
#define m 4
using namespace std;
 
// To calculate possible moves
int findPossibleMoves(int mat[n][m], int p, int q)
{
    // All possible moves of a knight
    int X[8] = { 2, 1, -1, -2, -2, -1, 1, 2 };
    int Y[8] = { 1, 2, 2, 1, -1, -2, -2, -1 };
 
    int count = 0;
 
    // Check if each possible move is valid or not
    for (int i = 0; i < 8; i++) {
 
        // Position of knight after move
        int x = p + X[i];
        int y = q + Y[i];
 
        // count valid moves
        if (x >= 0 && y >= 0 && x < n && y < m
            && mat[x][y] == 0)
            count++;
    }
 
    // Return number of possible moves
    return count;
}
 
// Driver program to check findPossibleMoves()
int main()
{
    int mat[n][m] = { { 1, 0, 1, 0 },
                      { 0, 1, 1, 1 },
                      { 1, 1, 0, 1 },
                      { 0, 1, 1, 1 } };
 
    int p = 2, q = 2;
 
    cout << findPossibleMoves(mat, p, q);
 
    return 0;
}

Java

// Java program to find number of possible moves of knight
public class Main {
public static final int n = 4;
public static final int m = 4;
 
    // To calculate possible moves
    static int findPossibleMoves(int mat[][], int p, int q)
    {
        // All possible moves of a knight
        int X[] = { 2, 1, -1, -2, -2, -1, 1, 2 };
        int Y[] = { 1, 2, 2, 1, -1, -2, -2, -1 };
 
        int count = 0;
 
        // Check if each possible move is valid or not
        for (int i = 0; i < 8; i++) {
 
            // Position of knight after move
            int x = p + X[i];
            int y = q + Y[i];
 
            // count valid moves
            if (x >= 0 && y >= 0 && x < n && y < m
                && mat[x][y] == 0)
                count++;
        }
 
        // Return number of possible moves
        return count;
    }
 
    // Driver program to check findPossibleMoves()
    public static void main(String[] args)
    {
        int mat[][] = { { 1, 0, 1, 0 },
                        { 0, 1, 1, 1 },
                        { 1, 1, 0, 1 },
                        { 0, 1, 1, 1 } };
 
        int p = 2, q = 2;
 
        System.out.println(findPossibleMoves(mat, p, q));
    }
}

Python3

# Python3 program to find number
# of possible moves of knight
n = 4;
m = 4;
 
# To calculate possible moves
def findPossibleMoves(mat, p, q):
    global n, m;
     
    # All possible moves of a knight
    X = [2, 1, -1, -2, -2, -1, 1, 2];
    Y = [1, 2, 2, 1, -1, -2, -2, -1];
 
    count = 0;
 
    # Check if each possible move
    # is valid or not
    for i in range(8):
         
        # Position of knight after move
        x = p + X[i];
        y = q + Y[i];
 
        # count valid moves
        if(x >= 0 and y >= 0 and x < n and
           y < m and mat[x][y] == 0):
            count += 1;
 
    # Return number of possible moves
    return count;
 
# Driver code
if __name__ == '__main__':
    mat = [[1, 0, 1, 0], [0, 1, 1, 1],
           [1, 1, 0, 1], [0, 1, 1, 1]];
 
    p, q = 2, 2;
 
    print(findPossibleMoves(mat, p, q));
 
# This code is contributed by 29AjayKumar

C#

// C# program to find number of
// possible moves of knight
using System;
 
class GFG
{
    static int n = 4;
    static int m = 4;
 
    // To calculate
    // possible moves
    static int findPossibleMoves(int [,]mat,
                                 int p, int q)
    {
        // All possible moves
        // of a knight
        int []X = { 2, 1, -1, -2,
                   -2, -1, 1, 2 };
        int []Y = { 1, 2, 2, 1,
                   -1, -2, -2, -1 };
 
        int count = 0;
 
        // Check if each possible
        // move is valid or not
        for (int i = 0; i < 8; i++)
        {
 
            // Position of knight
            // after move
            int x = p + X[i];
            int y = q + Y[i];
 
            // count valid moves
            if (x >= 0 && y >= 0 &&
                x < n && y < m &&
                mat[x, y] == 0)
                count++;
        }
 
        // Return number
        // of possible moves
        return count;
    }
 
    // Driver Code
    static public void Main ()
    {
        int [,]mat = { { 1, 0, 1, 0 },
                       { 0, 1, 1, 1 },
                       { 1, 1, 0, 1 },
                       { 0, 1, 1, 1 }};
 
        int p = 2, q = 2;
 
        Console.WriteLine(findPossibleMoves(mat,
                                            p, q));
    }
}
 
// This code is contributed by m_kit

PHP

= 0 && $y >= 0 &&
            $x < $n && $y < $m &&
            $mat[$x][$y] == 0)
            $count++;
    }
 
    // Return number
    // of possible moves
    return $count;
}
 
// Driver Code
$mat = array(array(1, 0, 1, 0),
             array(0, 1, 1, 1),
             array(1, 1, 0, 1),
             array(0, 1, 1, 1));
 
$p = 2; $q = 2;
 
echo findPossibleMoves($mat,
                       $p, $q);
 
// This code is contributed by ajit
?>

Javascript

输出：