厌氧程序

#include<bits/stdc++.h>
using namespace std;
#define int long long
int a[25][25],dp[25][25];
int safe(int x,int y,int xm,int ym){
	if(x==xm&&y==ym)
		return 0;
	int k1=max(abs(x-xm),abs(y-ym));
	int k2=min(abs(x-xm),abs(y-ym));
	if(k1==2&&k2==1) return 0;
	return 1;
}
signed main(){
	int xd,yd,xm,ym;
	cin>>xd>>yd>>xm>>ym;
	a[0][0]=1;
	for(int i=0;i<=xd;i++){
		for(int j=0;j<=yd;j++){
			if(safe(i,j,xm,ym)==0) a[i][j]=1;				
			else a[i][j]=0;		
		}
	}
	for(int i=0;i<=xd;i++){
		for(int j=0;j<=yd;j++){
			if(i==0&&j==0&&!a[i][j]) dp[i][j]=1;
			else if(a[i][j]==1) dp[i][j]=0;
			else dp[i][j]=dp[i-1][j]+dp[i][j-1];
		}
	}
	cout<<dp[xd][yd]<<endl;
	return 0;
}