{"id":92,"date":"2025-01-11T23:23:33","date_gmt":"2025-01-11T15:23:33","guid":{"rendered":"http:\/\/150.230.63.147\/blog\/?p=92"},"modified":"2025-01-11T23:23:33","modified_gmt":"2025-01-11T15:23:33","slug":"e-tree-reconstruction-%e8%a7%a3%e6%9e%90%e6%80%9d%e7%b6%ad","status":"publish","type":"post","link":"https:\/\/blog.seekrealthing.net\/blog\/?p=92","title":{"rendered":"E. Tree Reconstruction \u89e3\u6790(\u601d\u7dad)"},"content":{"rendered":"\n

Codeforce 1041 E. Tree Reconstruction \u89e3\u6790(\u601d\u7dad)<\/h1>\n

\u4eca\u5929\u6211\u5011\u4f86\u770b\u770bCF1041E\n\u984c\u76ee\u9023\u7d50<\/a><\/p>\n

\n

\u984c\u76ee<\/strong>\n\u7565\uff0c\u8acb\u76f4\u63a5\u770b\u539f\u984c<\/p>\n<\/blockquote>\n

\u524d\u8a00<\/h3>\n

\u4e00\u958b\u59cb\u5b8c\u5168\u641e\u932f\u984c\u76ee\u610f\u601d\uff0c\u9084\u4ee5\u70ba\u6bcf\u6b21\u6703\u522a\u9664\u4e00\u689d\u908a<\/p>\n

\u60f3\u6cd5<\/h3>\n

\u6ce8\u610f\u5230\u540c\u4e00\u500b\u9ede\u5c0d$(a_i,b_i)$\u5982\u679c\u51fa\u73fe$k$\u6b21\uff0c\u4ee3\u8868\u9019\u5169\u9ede\u4e2d\u9593\u6709$k$\u500b\u6bd4$a_i$\u5c0f\u7684\u9ede(\u8a18\u5f97$a_i<b_i$)\u3002\n\u90a3\u9ebc\u6211\u5011\u53ea\u8981\u5148\u628a\u6240\u6709\u9ede\u5c0d\u4fdd\u5b58\u8d77\u4f86(\u7d00\u9304\u51fa\u73fe\u6b21\u6578\u5728\u4e00\u500b$map$\u88e1)\uff0c\u4e26\u4e14\u8a18\u9304\u76ee\u524d\u9084\u53ef\u4ee5\u653e\u7684\u9ede\u5728\u4e00\u500b$vector<int>\\ remains$\u88e1\u3002\u6392\u5e8f\u9ede\u5c0d\u5f9e$a_i$\u6700\u5c0f\u7684\u9ede\u5c0d\u958b\u59cb\u904d\u6b77($a_i$\u6700\u5c0f\u7684\u9ede\u5c0d\u62ff\u6700\u5c0f\u7684\u9ede\u662f\u6700\u4fdd\u96aa\u7684):\u5c0d\u65bc\u4e00\u500b\u9ede\u5c0d$ii={a_i,b_i}$\uff0c\u6211\u5011\u770b\u770b\u76ee\u524d\u9084\u6709\u6c92\u6709\u8db3\u5920\u7684\uff0c\u6bd4$a_i$\u5c0f\u7684\u9ede\u5b58\u5728\u5728$remains$\u88e1\u53ef\u4ee5\u653e\u5230$a_i,b_i$\u7684\u4e2d\u9593(\u53ef\u4ee5\u4e8c\u5206\u641c)\uff0c\u82e5\u6c92\u6709\u5c31\u8f38\u51fa$NO$\u3002\n\u6700\u5f8c\u8981\u8003\u616e\u4e00\u500b\u60c5\u6cc1:\u5982\u679c\u4efb\u4f55\u4e00\u500b\u9ede\u5c0d$(a_i,b_i)$\u4e2d\u7684$b_i<n$\uff0c\u9019\u662f\u4e0d\u53ef\u80fd\u7684\uff0c\u76f4\u63a5\u8f38\u51fa$NO$\u3002(\u56e0\u6b64\uff0c\u5982\u679c\u6709\u89e3\u7684\u8a71\uff0c$n$\u9019\u500b\u9ede\u6703\u662f\u6240\u6709\u9ede\u5c0d\u7684$b_i$\uff0c\u6240\u4ee5\u4ee5\u4e0a\u7684\u5224\u65b7\u5c31\u5df2\u7d93\u8db3\u5920\u5224\u65b7\u6240\u6709\u7684$NO$\u7684\u60c5\u6cc1)<\/p>\n

\u7a0b\u5f0f\u78bc:<\/h3>\n
const int _n=1e5+10;\nint t,n,a,b;\nVI remains;\nvector<PII> e,in;\nmap<PII,int> mp;\nmain(void) {ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);\n  cin>>n;rep(i,0,n-1){cin>>a>>b;if(a>b)swap(a,b);mp[{a,b}]++;in.pb({a,b});}\n  rep(i,1,n+1)remains.pb(i); sort(all(in));\n  for(PII ii:in){\n    int tmp;\n    if(!mp[ii])continue;\n    if(ii.se<n){cout<<"NO\\n";return 0;}\n    if((tmp=upper_bound(all(remains),ii.fi-1)-remains.begin())<mp[ii]-1){cout<<"NO\\n";return 0;}\n    int prev=ii.fi;rep(i,tmp-mp[ii]+1,tmp)e.pb({prev,remains[i]}),prev=remains[i];\n    e.pb({prev,ii.se});\n    remains.erase(remains.begin()+tmp-mp[ii]+1,remains.begin()+tmp);\n    rep(i,0,SZ(remains))if(remains[i]==ii.fi||remains[i]==ii.se)remains.erase(remains.begin()+i);\n    mp[ii]=0;\n  }cout<<"YES\\n";for(PII ii:e)cout<<ii.fi<<' '<<ii.se<<'\\n';\n  return 0;\n}\n<\/code><\/pre>\n
\u6a19\u982d\u3001\u6a21\u677f\u8acb\u9edeSubmission\u770b\nSubmission<\/a><\/p>\n<\/div>\n","protected":false},"excerpt":{"rendered":"","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","enabled":false},"version":2}},"categories":[3],"tags":[10,9,8],"class_list":["post-92","post","type-post","status-publish","format-standard","hentry","category-ojcode","tag-codeforce","tag-ojcode","tag-8"],"jetpack_publicize_connections":[],"yoast_head":"\nE. 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