开int数组时g[i][j]可能是一个很奇怪的数，不一定是0。先弄一个for循环把所有的g[i][j]变成0
by code77playbridge @ 2020-08-11 10:33:19
```c
#include <bits/stdc++.h>
using namespace std;
int b1,b2,m1,m2;
long long f[40][40];
bool g[40][40];
int main(){
cin >> b1 >> b2 >> m1 >> m2;
memset(g,0,sizeof(g));
memset(f,0,sizeof(g));
g[m1][m2]=1;
if(m1-1>=0&&m1-2>=0) g[m1-1][m2-2]=1;
if(m1+1<=b1&&m2-2>=0) g[m1+1][m2-2]=1;
if(m1-2>=0&&m2-1>=0) g[m1-2][m2-1]=1;
if(m1+2<=b1&&m2-1>=0) g[m1+2][m2-1]=1;
if(m1-1>=0&&m2+2<=b2) g[m1-1][m2+2]=1;
if(m1-2>=0&&m2+1<=b2) g[m1-2][m2+1]=1;
if(m1+1<=b1&&m2+2<=b2) g[m1+1][m2+2]=1;
if(m1+2<=b1&&m2+1<=b2) g[m1+2][m2+1]=1;
for(int i=0;i<=b1;i++){
for(int j=0;j<=b2;j++){
if(!g[i][j]){
if(i==0&j==0) f[0][0]=1;
else if(i>0&&j==0)f[i][0]=f[i-1][0];
else if(i==0&&j>0) f[0][j]=f[0][j-1];
else f[i][j]=f[i-1][j]+f[i][j-1];
}
}
}
printf("%d",f[b1][b2]);
return 0;
}
```
三AC代码，这又错哪了
by 2020yhq @ 2020-08-11 10:48:53
```
if(i==0&&j==0) f[0][0]=1;
```
by WTR2007 @ 2020-08-12 18:59:47
~~全局变量好像会自动赋0~~
by zty_luogu @ 2020-08-15 23:24:05