我使用的是dfs算法

#include <iostream>
#include <cstring>
using namespace std;

int P1002_ANS = 0;
int bx,by,hx,hy;
bool map[20][20];

void P1002_dfs(int x,int y){
    if (x==bx&&y==by){P1002_ANS++;return;}
    else if (x>bx||y>by) return;
    if (map[x+1][y]!=false&&!(x+1>bx)&&!(y>by)) P1002_dfs(x+1,y);
    if (map[x][y+1]!=false&&!(x>bx)&&!(y+1>by)) P1002_dfs(x,y+1);
}

int main(){
    cin >> bx >> by >> hx >> hy;
    memset(map, true, sizeof(map));
    map[hx][hy] = map[hx-1][hy-2] = map[hx-2][hy-1] = map[hx-2][hy+1] =
    map[hx-1][hy+2] = map[hx+1][hy+2] = map[hx+2][hy+1] = map[hx+2][hy-1] =
    map[hx+1][hy-2] = false;
    P1002_dfs(0,0);
    cout << P1002_ANS << endl;
    return 0;
}