\u56e0\u4e3a\u7ef4\u62a4\u7684\u662f\u504f\u5e8f\u5173\u7cfb\uff0c\u5f88\u5bb9\u6613\u53ef\u4ee5\u53d1\u73b0\u662f\u62d3\u6251\u6392\u5e8f\u88f8\u9898\u3002
\n\u4e00\u4e2a\u5b57\u6bcd\u5199\u9519\u4e86\u8c03\u4e86\u534a\u5929\u3002
\n\u53ef\u4ee5\u7528\u5806\u7ef4\u62a4\u5b57\u5178\u5e8f\u3002<\/p>\n
\r\n#include<iostream>\r\n#include<cstdio>\r\n#include<queue>\r\n#include<cstring>\r\n#include<vector>\r\nusing namespace std;\r\n#define Min(_A,_B) ((_A)<(_B)?(_A):(_B))\r\n\r\nint in[30],n,len[1005],at=0,ss[30];\r\nbool mp[30][30];\r\nchar ch[105][105];\r\nchar ans[30];\r\ninline void CMP(const int &A,const int &B){\r\n int le=Min(len[A],len[B]);\r\n for(int i=1;i<=le;++i){\r\n if(ch[A][i]!=ch[B][i]){\r\n if(!mp[ch[A][i]-'a'][ch[B][i]-'a']){\r\n mp[ch[A][i]-'a'][ch[B][i]-'a']=1;\r\n ++in[ch[B][i]-'a'];\r\n }\r\n return;\r\n }\r\n }\r\n if(len[A]>len[B]){\r\n puts(\"Impossible\");\r\n exit(0);\r\n }\r\n}\r\npriority_queue< int,vector<int>,greater<int> > q;\r\ninline void srt(){\r\n for(int i=0;i<26;++i){\r\n if(!in[i]){\r\n q.push(i);\r\n }\r\n }\r\n int p;\r\n while(!q.empty()){\r\n p=q.top();\r\n q.pop();\r\n ans[++at]=p+'a';\r\n for(int i=0;i<26;++i){\r\n if(mp[p][i]){\r\n --in[i];\r\n if(!in[i]){\r\n q.push(i);\r\n }\r\n }\r\n }\r\n }\r\n if(at<26){\r\n puts(\"Impossible\");\r\n exit(0);\r\n }\r\n ans[++at]='\\0';\r\n}\r\nvoid init(){\r\n scanf(\"%d\",&n);\r\n memset(mp,0,sizeof(mp));\r\n memset(in,0,sizeof(in));\r\n for(int i=1;i<=n;++i){\r\n cin>>ch[i]+1;\r\n len[i]=strlen(ch[i]+1);\r\n }\r\n for(int i=1;i<n;++i){\r\n CMP(i,i+1);\r\n }\r\n srt(); \r\n cout<<ans+1;\r\n}\r\nint main(){\r\n init();\r\n return 0;\r\n}<\/code><\/pre>\n <\/p>\n","protected":false},"excerpt":{"rendered":"
\u56e0\u4e3a\u7ef4\u62a4\u7684\u662f\u504f\u5e8f\u5173\u7cfb\uff0c\u5f88\u5bb9\u6613\u53ef\u4ee5\u53d1\u73b0\u662f\u62d3\u6251\u6392\u5e8f\u88f8\u9898\u3002 \u4e00\u4e2a\u5b57\u6bcd\u5199\u9519\u4e86\u8c03\u4e86\u534a\u5929\u3002 \u53ef\u4ee5\u7528\u5806\u7ef4\u62a4\u5b57\u5178\u5e8f\u3002 #inc … <\/p>\n