【回溯法】马拦过河卒

#include <iostream>
#include <cstring>

using namespace std;
long long f[25][25];
int a[25][25],m,n,x,y;
int zx[8]={-2,-1,1,2,2,1,-1,-2},zy[8]={-1,-2,-2,-1,1,2,2,1};
int main()
{
    cin>>n>>m>>x>>y;
    memset(f,0,sizeof(f));
    memset(a,0,sizeof(a));
    a[x+1][y+1]=1;
    for(int i=0;i<8;i++)
    {
        if(x+zx[i]>=0&&y+zy[i]>=0)
            a[x+zx[i]+1][y+zy[i]+1]=1;
    }

    f[1][1]=1;
    for(int i=1;i<=n+1;i++)
    {
        for(int j=1;j<=m+1;j++)
        {
            if(i==1&&j==1)  continue;
            if(a[i][j]==1)  continue;
            f[i][j]=f[i-1][j]+f[i][j-1];
        }
    }
    cout<<f[n+1][m+1]<<endl;
    return 0;
}