二、設計思想

　　首先將所有點設定為可通行，將控制點設定為不可通行。因為只可以向下或者向右行走，所以要想到達目標點只需要到達其左邊的點或者上邊的點，以此類推，計算從起點到達中間任何一個點的路徑條數，並用陣列tripnum[][]儲存到達這個點的路徑條數。

三、程式碼

#include<iostream>
#include<cstdio>
using namespace std;
int main()
{
    int a[9] = { 0,-1,-1,-2,-2,1,1,2,2 };
    int b[9] = { 0,2,-2,1,-1,2,-2,1,-1 };
    
 
int map[16][16] = { 0 };
    long long tripnum[16][16] = { 0 };
    int n, m, x, y;
    scanf_s("%d %d %d %d", &n, &m, &x, &y);
    for (int i = 0; i < 16; i++)
        for (int j = 0; j < 16; j++)
            map[i][j] = 1;
    for (int i = 0; i < 9; i++)
    {
        if (x + a[i] <= 15
 
 && x + a[i] >= 0 && y + b[i] <= 15 && y + b[i] >= 0)
            map[x + a[i]][y + b[i]] = 0;
    }
    for (int i = 0; i < 16; i++)
    {
        if (map[0][i] == 1)
        {
            tripnum[0][i] = 1;
        }
        else
            break;
    }
    for (int i = 0
 
; i < 16; i++)
    {
        if (map[i][0] == 1)
        {
            tripnum[i][0] = 1;
        }
        else
            break;
    }
    for (int i = 1; i <= n; i++)
    {
        for (int j = 1; j <= m; j++)
        {
            if (map[i][j] == 1)
                tripnum[i][j] = tripnum[i - 1][j] +
                tripnum[i][j - 1];
        }
    }
    printf("%lld", tripnum[n][m]);
    return 0;
}