50pts求调，悬赏关注

#include<bits/stdc++.h>
using namespace std;
const int N=30;
#define int long long
#define pb emplace_back
vector<int> g[N];
int n,m,a[N][N],ind[N],d[N],ans[N],vis[N],b[N][N];
queue<int> q;
signed main(){
	ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
	cin>>n>>m;
	for(int h=1;h<=m;h++){
		string s;
		cin>>s;
        memset(vis,0,sizeof(vis));
        int u=s[0]-'A',v=s[2]-'A';
		a[u][v]=1;
		b[u][v]=1;
		g[u].pb(v);
		ind[v]++;d[v]++;
		int p=0;
		for(int i=0;i<n;i++) if(!ind[i]&&g[i].size()) q.push(i),ans[++p]=i,vis[i]=1;
        bool f=p;
		while(q.size()){
            if(q.size()!=1) f=0;
			int x=q.front();q.pop();
			for(int y:g[x]){
				a[x][y]=0;
				ind[y]--;
				if(!ind[y]&&!vis[y]) q.push(y),ans[++p]=y,vis[y]=1;
			}
			g[x].clear();
		}
        for(int i=0;i<n;i++){
            if(ind[i]){
                cout<<"Inconsistency found after "<<h<<" relations.";
                return 0;
            }
        }
		if(p==n&&f){
			cout<<"Sorted sequence determined after "<<h<<" relations: ";
			for(int i=1;i<=p;i++) cout<<char(ans[i]+'A');
			cout<<'.';
			return 0;
		}
		for(int i=0;i<n;i++) ind[i]=d[i];
		for(int i=0;i<n;i++){
			for(int j=0;j<n;j++){
				if(b[i][j]&&!a[i][j]){
					a[i][j]=1;
					g[i].pb(j);
				}
			}
		}
	}
	cout<<"Sorted sequence cannot be determined.";
	return 0;
}