改后AC代码:
```cpp
#include<bits/stdc++.h>
using namespace std;
int ans[1001][1001];
bool notok[1001][1001];
const int dx[4]={1,-1,0,0};
const int dy[4]={0,0,-1,1};
struct Node
{
int x,y;
Node(int _x,int _y)
{
x=_x,y=_y;
}
};
string str;
int main()
{
// freopen("data.in","r",stdin);
memset(ans,-1,sizeof(ans));
queue<Node> s;
int n;
cin>>n;
int m=n;
for(int i=1;i<=n;i++){
cin>>str;
for(int j=0;j<n;++j)
notok[i][j+1]=str[j]-48;
}
int x,y,x1,y1;
cin>>x>>y>>x1>>y1;
Node first(x,y);
s.push(first);
ans[x][y]=0;
while(!s.empty())
{
Node now=s.front();s.pop();
int _x=now.x,_y=now.y,step=ans[_x][_y];
for(int i=0;i<=3;i++)
{
int xx=_x+dx[i],yy=_y+dy[i];
if(xx>=1&&xx<=n&&yy>=1&&yy<=m&&ans[xx][yy]==-1&&!notok[xx][yy])
{
Node newnode(xx,yy);
s.push(newnode);
ans[xx][yy]=step+1;
}
}
}
cout<<ans[x1][y1]<<"\n";
}
```
主要改动:
1. 采用$string$读入01串,再转成$bool$数组
2. $BFS$转移仅上下左右移动$4$个方向,故循环为$0\rightarrow 3$
另外,不建议使用$y_1$这种变量名,容易撞保留字(其在$math.h$中是一个被定义的变量)
给一份我写的代码
```cpp
#include<bits/stdc++.h>
using namespace std;
struct Node{
int x,y,s;
}s,t;
int n,dx[4]={0,0,1,-1},dy[4]={1,-1,0,0};
bool g[1010][1010];
string str;
queue<Node> q;
void BFS(){
g[s.x][s.y]=1;
q.push(s);
while(!q.empty()){
Node now=q.front();q.pop();
for(int i=0;i<4;++i){
int nx=now.x+dx[i],ny=now.y+dy[i];
if(nx==t.x&&ny==t.y){
cout<<now.s+1<<"\n";
exit(0);
}
if(nx>0&&nx<=n&&ny>0&&ny<=n&&!g[nx][ny]){
g[nx][ny]=1;
q.push((Node){nx,ny,now.s+1});
}
}
}
}
signed main(){
ios::sync_with_stdio(false);
cin.tie(0),cout.tie(0);
// freopen("data.in","r",stdin);
cin>>n;
for(int i=1;i<=n;++i){
cin>>str;
for(int j=0;j<n;++j)
g[i][j+1]=str[j]-48;
}
cin>>s.x>>s.y>>t.x>>t.y;
BFS();
return 0;
}
```
by DNWy @ 2021-11-15 07:52:12
多谢大佬！！！！
by Li_wenjie @ 2021-11-16 21:57:29