被坑了一手
起点要标记
dfs
https://www.luogu.org/problemnew/show/P1605
#include<cstdio>
#include<cstring>
#include<string.h>
#include<algorithm>
#include<iostream>
#include<stdlib.h>
using namespace std;
const int inf=0x3f3f3f3f;
const int maxn=1000000;
int a[500][500];
int vis[500][500];
int dx[]={-1,1,0,0};
int dy[]={0,0,1,-1};
int n,m,t;
int sx,sy;
int ex,ey;
int ans=0;
bool judge(int x,int y){
if(x>=1&&x<=n&&y>=1&&y<=m&&!vis[x][y]&&a[x][y]!=2){
return true;
}
return false;
}
void dfs(int x,int y){
if(x==ex&&y==ey){
ans++;
return ;
}
for(int i=0;i<4;i++){
int nx=x+dx[i];
int ny=y+dy[i];
if(judge(nx,ny)){
vis[nx][ny]=1;
dfs(nx,ny);
vis[nx][ny]=0;
}
}
}
int main(){
cin>>n>>m>>t;
for(int i=1;i<=n;i++){
for(int j=1;j<=m;j++){
a[i][j]=0;
}
}
cin>>sx>>sy>>ex>>ey;
while(t--){
int x,y;
cin>>x>>y;
a[x][y]=2;
}
vis[sx][sy]=1;
dfs(sx,sy);
cout<<ans<<endl;
}