rt，不知道哪里有问题：

#include<bits/stdc++.h> 
using namespace std;
const int size=1e7+10;
int n,m,stx,sty,edx,edy,ans=0x3f3f3f3f;
char a[510][510];
int dx[]={0,-1,0,1,0};
int dy[]={0,0,-1,0,1};
inline int encode(int t,int x,int y){return (t-1)*m*n+(x-1)*m+y;}
int tot=0,ver[size],edge[size],nxt[size],head[size];
int totpoint=n*m*4;
inline void add(int x,int y,int z){ver[++tot]=y,edge[tot]=z,nxt[tot]=head[x],head[x]=tot;}
int d[size],v[size];
priority_queue<pair<int,int>,vector<pair<int,int> >,greater<pair<int,int> > > q;
inline void dijkstra(int s){
	//memset(d,0x3f,sizeof(d));
	for(int i=1;i<=n*m*4;++i) d[i]=0x3f3f3f3f;
	d[s]=0;q.push(make_pair(0,s));
	while(!q.empty()){
		int x=q.top().second;q.pop();
		if(v[x]) continue;
		v[x]=1;
		for(int i=head[x];i;i=nxt[i]){
			int y=ver[i],z=edge[i];
			if(d[y]>d[x]+z){
				d[y]=d[x]+z;
				q.push(make_pair(d[y],y));
			}
		}
	}	
}
int main(){
	ios::sync_with_stdio(0);
	cin>>m>>n;
	bool flag=true;
	for(int i=1;i<=n;++i){
		string s;
		cin>>s;
		int len=s.length();
		for(int j=0;j<len;++j){
			a[i][j+1]=s[j];
			if(flag&&s[j]=='C') stx=i,sty=j+1,flag=false;
			if(!flag&&s[j]=='C') edx=i,edy=j+1;
		}
	}
	for(int k=0;k<=4;++k) for(int i=1;i<=n;++i) for(int j=1;j<=m;++j){
		int nx=i+dx[k],ny=j+dy[k];
		if(nx<1||nx>n||ny<1||ny>m) continue;
		if(a[i][j]=='*'||a[nx][ny]=='*') continue;
		add(encode(k,i,j),encode(k,nx,ny),0);
	}
	for(int i=1;i<=n;++i) for(int j=1;j<=m;++j) if(a[i][j]!='*') for(int pos1=1;pos1<=4;++pos1) for(int pos2=1;pos2<=4;++pos2) if(pos1!=pos2) add(encode(pos1,i,j),encode(pos2,i,j),1);
	for(int k=1;k<=4;++k){
		dijkstra(encode(k,stx,sty));
		for(int kk=1;kk<=4;++kk) ans=min(ans,d[encode(kk,edx,edy)]);
	}
	cout<<ans<<endl;
	return 0;
}

这是20分，但是输出 ans-1有80分（？）

求助大佬们/kel