求助P14273

#include<bits/stdc++.h>
using namespace std;
int n,m,ans=0,indeg[2005][2005];
char a[2005][2005]; 
vector< pair<int,int> > dep[2005][2005];
queue< pair<int,int> > q;
void solve(int x,int y){
	if(a[x][y]=='.') return;
	int xx=0,yy=0;
	if(a[x][y]=='N') xx=-1;
	else if(a[x][y]=='S') xx=1;
	else if(a[x][y]=='E') yy=1;
	else if(a[x][y]=='W') yy=-1;
	int nx=x+xx,ny=y+yy;
	while(nx>=1&&ny>=1&&nx<=n&&ny<=m){
		if(a[nx][ny]!='.'){
			dep[nx][ny].push_back({x,y});
			indeg[x][y]++;
		}
		nx+=xx;
		ny+=yy;
	}
}
int main(){
    scanf("%d%d",&n,&m);
    for(int i=1;i<=n;++i)
    	for(int j=1;j<=m;++j) cin>>a[i][j];
	for(int i=1;i<=n;++i)
		for(int j=1;j<=m;++j) solve(i,j);
	for(int i=1;i<=n;++i)
		for(int j=1;j<=m;++j)
			if(a[i][j]!='.'&&indeg[i][j]==0){
				q.push(make_pair(i,j));
				a[i][j]='.';
			}
	while(!q.empty()){
		int x=q.front().first,y=q.front().second;
		q.pop();
		ans++;
		for(int i=0;i<dep[x][y].size();++i){
			int xx=dep[x][y][i].first,yy=dep[x][y][i].second;
			indeg[xx][yy]--;
			if(a[xx][yy]!='.'&&indeg[xx][yy]==0){
				q.push(make_pair(xx,yy));
				a[xx][yy]='.';
			}
		}
	}
	cout<<ans;
    return 0;
}