看到一个代码,几乎完美,我都不想改了。。以后当模板
#include <iostream> #include <string> #include <vector> #include <queue> using namespace std; int n,m; vector<int> top; vector<int> in; vector< vector<int> > map; int topsort(){ int i,u; bool flag=false; queue<int> q; vector<int> d(in.begin(),in.end()); for(i=0;i<n;i++) if(!d[i]) q.push(i); top.clear(); while(!q.empty()){ if(q.size()!=1) flag=true; u=q.front(); q.pop(); top.push_back(u); for(i=0;i<map[u].size();i++) if(--d[map[u][i]]==0) q.push(map[u][i]); } if(top.size()!=n) return 1; if(flag) return 0; return 2; } int main(){ string str; int i,j,u,v,ans; while(cin>>n>>m,n||m){ in.assign(n,0); map.assign(n,vector<int>()); for(ans=i=0;i<m && !ans;i++){ cin>>str; u=str[0]-'A',v=str[2]-'A'; if(find(map[u].begin(),map[u].end(),v)==map[u].end()) map[u].push_back(v),in[v]++; ans=topsort(); } for(j=i;j<m;j++) cin>>str; switch(ans){ case 0:cout<<"Sorted sequence cannot be determined."<<endl;break; case 1:cout<<"Inconsistency found after "<<i<<" relations."<<endl;break; case 2:{ cout<<"Sorted sequence determined after "<<i<<" relations: "; for(j=0;j<n;j++) cout<<char('A'+top[j]); cout<<"."<<endl; break; } } } return 0; }
代码转自:http://www.cppblog.com/mythit/archive/2009/05/19/83406.html
题意原来是,如果到第几个relations
的时候,出了那三种结果里的哪一种,后面的就可以忽略了。。