{"id":49,"date":"2025-01-11T22:57:59","date_gmt":"2025-01-11T14:57:59","guid":{"rendered":"http:\/\/150.230.63.147\/blog\/?p=49"},"modified":"2025-01-11T22:57:59","modified_gmt":"2025-01-11T14:57:59","slug":"b-two-fairs-%e8%a7%a3%e6%9e%90%e6%80%9d%e7%b6%ad%e3%80%81dfs%e3%80%81%e7%b5%84%e5%90%88","status":"publish","type":"post","link":"https:\/\/blog.seekrealthing.net\/blog\/?p=49","title":{"rendered":"B. Two Fairs \u89e3\u6790(\u601d\u7dad\u3001DFS\u3001\u7d44\u5408)"},"content":{"rendered":"\n

Codeforce 1276 B. Two Fairs \u89e3\u6790(\u601d\u7dad\u3001DFS\u3001\u7d44\u5408)<\/h1>\n

\u4eca\u5929\u6211\u5011\u4f86\u770b\u770bCF1276B
\n\u984c\u76ee\u9023\u7d50<\/a><\/p>\n

\n

\u984c\u76ee<\/strong>
\n\u7d66\u4e00\u500b\u9023\u901a\u5716\uff0c\u4e26\u7d66\u5169\u500b\u9ede($a,b$)\uff0c\u6c42\u6709\u591a\u5c11\u9ede\u5c0d\u4f7f\u5f97:\u4efb\u4e00\u8def\u5f91\u90fd\u8981\u7d93\u904e$a,b$\u9019\u5169\u9ede\u3002<\/p>\n<\/blockquote>\n

\u60f3\u6cd5<\/h3>\n

\u9996\u5148\u56e0\u70ba\u4e0d\u4e00\u5b9a\u662f\u68f5\u6a39\uff0c\u6240\u4ee5\u7e3d\u89ba\u5f97LCA\u7528\u4e0d\u5230\u3002\u800c\u9019\u500b\u5716\u53c8\u5f88\u5927\uff0c\u56e0\u6b64\u611f\u89ba\u61c9\u8a72\u662f\u8981\u5f9e$a,b$\u9019\u5169\u9ede\u51fa\u767c\u505a\u9ede\u4e8b\u60c5\uff0c\u4f8b\u5982DFS\u3002
\n\u7576\u958b\u59cb\u9019\u6a23\u60f3\u4ee5\u5f8c\uff0c\u6703\u767c\u73fe\u6211\u5011\u5176\u5be6\u53ef\u4ee5\u628a\u6240\u6709\u9ede\u5206\u6210\u4e09\u7a2e\u985e\u578b:<\/p>\n

    \n
  1. $a,b$\u90fd\u8d70\u5f97\u5230\u7684<\/li>\n
  2. \u53ea\u6709$a$\u8d70\u5f97\u5230<\/li>\n
  3. \u53ea\u6709$b$\u8d70\u5f97\u5230<\/li>\n<\/ol>\n

    \u9019\u6a23\u6700\u5f8c\u7684\u9ede\u5c0d\u6578\u91cf\u5c31\u662f2\u985e\u4e58\u4ee53\u985e\u3002
    \n\u5be6\u4f5c\u8d77\u4f86\u53ea\u8981\u5f9e$a,b$\u5206\u5225DFS\u4e00\u6b21\uff0c\u4e0d\u59a8\u5047\u8a2d\u6211\u5011\u73fe\u5728\u662f\u5f9e$a$\u958b\u59cbDFS:
    \n\u90a3\u9ebc\u53ea\u8981\u9047\u5230$b$\u6642\u7576\u524d\u8def\u5f91\u7684DFS\u505c\u4e0b\u4f86\uff0c\u9019\u6a23\u90a3\u4e9b\u4e00\u5b9a\u8981\u7d93\u904e$b$\u624d\u80fd\u5230\u7684\u9ede\u5c31\u4e0d\u53ef\u80fd\u8a2a\u554f\u5230\u4e86\u3002
    \n\u800c\u5340\u5206\u4ee5\u4e0a\u4e09\u7a2e\u985e\u578b\u7684\u9ede\uff0c\u53ea\u8981\u7dad\u8b77\u4e00\u500b\u9663\u5217(\u7d66\u6bcf\u500b\u9ede\u4e00\u500b\u6578\u5b57)\uff0c\u5728\u5f9e$a$\u958b\u59cbDFS\u6642\uff0c\u7d93\u904e\u7684\u9ede\u90fd\u52a0\u4e0a$1$\uff1b\u5f9e$b$\u958b\u59cbDFS\u6642\uff0c\u7d93\u904e\u7684\u9ede\u90fd\u52a0\u4e0a$2$\u3002\u4ee5\u4e0a\u5c31\u53ef\u4ee5\u5340\u5206\u5404\u7a2e\u9ede\u4e86\u3002<\/p>\n

    \u7a0b\u5f0f\u78bc:<\/h3>\n
    const int _n=2e5+10;  \nint t,n,m,a,b,u,v,ans[_n],cnt[4];  \nVI G[_n];  \nbool vis[_n];  \nvoid dfs(int v,int end,int val){  \n  if(v==end)return; vis[v]=1; if(v!=a and v!=b)ans[v]+=val;  \n  rep(i,0,SZ(G[v]))if(!vis[G[v][i]])dfs(G[v][i],end,val);  \n}  \nmain(void) {cin.tie(0);ios_base::sync_with_stdio(0);  \n  cin>>t;while(t--){  \n    memset(vis,0,sizeof vis); rep(i,1,n+1)G[i].clear();  \n    memset(ans,0,sizeof ans); memset(cnt,0,sizeof cnt);  \n    cin>>n>>m>>a>>b;rep(i,0,m){cin>>u>>v;G[u].pb(v),G[v].pb(u);}  \n    dfs(a,b,1); memset(vis,0,sizeof vis); dfs(b,a,2);  \n    rep(i,1,n+1)cnt[ans[i]]++;  \n    cout<<1ll*cnt[1]*cnt[2]<<'\\n';  \n  }  \n  return 0;  \n}  \n<\/code><\/pre>\n
    \u6a19\u982d\u3001\u6a21\u677f\u8acb\u9edeSubmission\u770b
    \n    Submission<\/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":[7,8,6],"class_list":["post-49","post","type-post","status-publish","format-standard","hentry","category-ojcode","tag-dfs","tag-8","tag-6"],"jetpack_publicize_connections":[],"yoast_head":"\nB. Two Fairs \u89e3\u6790(\u601d\u7dad\u3001DFS\u3001\u7d44\u5408) - Logic Formatting<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/blog.seekrealthing.net\/blog\/?p=49\" \/>\n<meta property=\"og:locale\" content=\"zh_TW\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"B. Two Fairs \u89e3\u6790(\u601d\u7dad\u3001DFS\u3001\u7d44\u5408) - Logic Formatting\" \/>\n<meta property=\"og:url\" content=\"https:\/\/blog.seekrealthing.net\/blog\/?p=49\" \/>\n<meta property=\"og:site_name\" content=\"Logic Formatting\" \/>\n<meta property=\"article:published_time\" content=\"2025-01-11T14:57:59+00:00\" \/>\n<meta name=\"author\" content=\"jeff\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"\u4f5c\u8005:\" \/>\n\t<meta name=\"twitter:data1\" content=\"jeff\" \/>\n\t<meta name=\"twitter:label2\" content=\"\u9810\u4f30\u95b1\u8b80\u6642\u9593\" \/>\n\t<meta name=\"twitter:data2\" content=\"1 \u5206\u9418\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\/\/blog.seekrealthing.net\/blog\/?p=49#article\",\"isPartOf\":{\"@id\":\"https:\/\/blog.seekrealthing.net\/blog\/?p=49\"},\"author\":{\"name\":\"jeff\",\"@id\":\"https:\/\/blog.seekrealthing.net\/blog\/#\/schema\/person\/233e80a0fee3d4706f067f2e88c0b454\"},\"headline\":\"B. Two Fairs \u89e3\u6790(\u601d\u7dad\u3001DFS\u3001\u7d44\u5408)\",\"datePublished\":\"2025-01-11T14:57:59+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\/\/blog.seekrealthing.net\/blog\/?p=49\"},\"wordCount\":37,\"commentCount\":0,\"publisher\":{\"@id\":\"https:\/\/blog.seekrealthing.net\/blog\/#organization\"},\"keywords\":[\"DFS\",\"\u601d\u7dad\",\"\u7d44\u5408\"],\"articleSection\":[\"ojcode\"],\"inLanguage\":\"zh-TW\",\"potentialAction\":[{\"@type\":\"CommentAction\",\"name\":\"Comment\",\"target\":[\"https:\/\/blog.seekrealthing.net\/blog\/?p=49#respond\"]}]},{\"@type\":\"WebPage\",\"@id\":\"https:\/\/blog.seekrealthing.net\/blog\/?p=49\",\"url\":\"https:\/\/blog.seekrealthing.net\/blog\/?p=49\",\"name\":\"B. Two Fairs \u89e3\u6790(\u601d\u7dad\u3001DFS\u3001\u7d44\u5408) - Logic Formatting\",\"isPartOf\":{\"@id\":\"https:\/\/blog.seekrealthing.net\/blog\/#website\"},\"datePublished\":\"2025-01-11T14:57:59+00:00\",\"breadcrumb\":{\"@id\":\"https:\/\/blog.seekrealthing.net\/blog\/?p=49#breadcrumb\"},\"inLanguage\":\"zh-TW\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\/\/blog.seekrealthing.net\/blog\/?p=49\"]}]},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\/\/blog.seekrealthing.net\/blog\/?p=49#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"\u9996\u9801\",\"item\":\"https:\/\/blog.seekrealthing.net\/blog\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"B. Two Fairs \u89e3\u6790(\u601d\u7dad\u3001DFS\u3001\u7d44\u5408)\"}]},{\"@type\":\"WebSite\",\"@id\":\"https:\/\/blog.seekrealthing.net\/blog\/#website\",\"url\":\"https:\/\/blog.seekrealthing.net\/blog\/\",\"name\":\"Logic Formatting\",\"description\":\"\",\"publisher\":{\"@id\":\"https:\/\/blog.seekrealthing.net\/blog\/#organization\"},\"potentialAction\":[{\"@type\":\"SearchAction\",\"target\":{\"@type\":\"EntryPoint\",\"urlTemplate\":\"https:\/\/blog.seekrealthing.net\/blog\/?s={search_term_string}\"},\"query-input\":{\"@type\":\"PropertyValueSpecification\",\"valueRequired\":true,\"valueName\":\"search_term_string\"}}],\"inLanguage\":\"zh-TW\"},{\"@type\":\"Organization\",\"@id\":\"https:\/\/blog.seekrealthing.net\/blog\/#organization\",\"name\":\"Logic Formatting\",\"url\":\"https:\/\/blog.seekrealthing.net\/blog\/\",\"logo\":{\"@type\":\"ImageObject\",\"inLanguage\":\"zh-TW\",\"@id\":\"https:\/\/blog.seekrealthing.net\/blog\/#\/schema\/logo\/image\/\",\"url\":\"https:\/\/blog.seekrealthing.net\/blog\/wp-content\/uploads\/2025\/02\/android-chrome-512x512-1.png\",\"contentUrl\":\"https:\/\/blog.seekrealthing.net\/blog\/wp-content\/uploads\/2025\/02\/android-chrome-512x512-1.png\",\"width\":512,\"height\":512,\"caption\":\"Logic Formatting\"},\"image\":{\"@id\":\"https:\/\/blog.seekrealthing.net\/blog\/#\/schema\/logo\/image\/\"}},{\"@type\":\"Person\",\"@id\":\"https:\/\/blog.seekrealthing.net\/blog\/#\/schema\/person\/233e80a0fee3d4706f067f2e88c0b454\",\"name\":\"jeff\",\"image\":{\"@type\":\"ImageObject\",\"inLanguage\":\"zh-TW\",\"@id\":\"https:\/\/blog.seekrealthing.net\/blog\/#\/schema\/person\/image\/\",\"url\":\"https:\/\/secure.gravatar.com\/avatar\/f9b571b28c252728386f0002b35d9cb9a9028f740b0f9ca5ad678e7eb21c4857?s=96&d=mm&r=g\",\"contentUrl\":\"https:\/\/secure.gravatar.com\/avatar\/f9b571b28c252728386f0002b35d9cb9a9028f740b0f9ca5ad678e7eb21c4857?s=96&d=mm&r=g\",\"caption\":\"jeff\"},\"sameAs\":[\"http:\/\/150.230.63.147\/blog\"],\"url\":\"https:\/\/blog.seekrealthing.net\/blog\/?author=1\"}]}<\/script>\n<!-- \/ Yoast SEO plugin. -->","yoast_head_json":{"title":"B. Two Fairs \u89e3\u6790(\u601d\u7dad\u3001DFS\u3001\u7d44\u5408) - Logic Formatting","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/blog.seekrealthing.net\/blog\/?p=49","og_locale":"zh_TW","og_type":"article","og_title":"B. Two Fairs \u89e3\u6790(\u601d\u7dad\u3001DFS\u3001\u7d44\u5408) - Logic Formatting","og_url":"https:\/\/blog.seekrealthing.net\/blog\/?p=49","og_site_name":"Logic Formatting","article_published_time":"2025-01-11T14:57:59+00:00","author":"jeff","twitter_card":"summary_large_image","twitter_misc":{"\u4f5c\u8005:":"jeff","\u9810\u4f30\u95b1\u8b80\u6642\u9593":"1 \u5206\u9418"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"Article","@id":"https:\/\/blog.seekrealthing.net\/blog\/?p=49#article","isPartOf":{"@id":"https:\/\/blog.seekrealthing.net\/blog\/?p=49"},"author":{"name":"jeff","@id":"https:\/\/blog.seekrealthing.net\/blog\/#\/schema\/person\/233e80a0fee3d4706f067f2e88c0b454"},"headline":"B. Two Fairs \u89e3\u6790(\u601d\u7dad\u3001DFS\u3001\u7d44\u5408)","datePublished":"2025-01-11T14:57:59+00:00","mainEntityOfPage":{"@id":"https:\/\/blog.seekrealthing.net\/blog\/?p=49"},"wordCount":37,"commentCount":0,"publisher":{"@id":"https:\/\/blog.seekrealthing.net\/blog\/#organization"},"keywords":["DFS","\u601d\u7dad","\u7d44\u5408"],"articleSection":["ojcode"],"inLanguage":"zh-TW","potentialAction":[{"@type":"CommentAction","name":"Comment","target":["https:\/\/blog.seekrealthing.net\/blog\/?p=49#respond"]}]},{"@type":"WebPage","@id":"https:\/\/blog.seekrealthing.net\/blog\/?p=49","url":"https:\/\/blog.seekrealthing.net\/blog\/?p=49","name":"B. Two Fairs \u89e3\u6790(\u601d\u7dad\u3001DFS\u3001\u7d44\u5408) - Logic Formatting","isPartOf":{"@id":"https:\/\/blog.seekrealthing.net\/blog\/#website"},"datePublished":"2025-01-11T14:57:59+00:00","breadcrumb":{"@id":"https:\/\/blog.seekrealthing.net\/blog\/?p=49#breadcrumb"},"inLanguage":"zh-TW","potentialAction":[{"@type":"ReadAction","target":["https:\/\/blog.seekrealthing.net\/blog\/?p=49"]}]},{"@type":"BreadcrumbList","@id":"https:\/\/blog.seekrealthing.net\/blog\/?p=49#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"\u9996\u9801","item":"https:\/\/blog.seekrealthing.net\/blog"},{"@type":"ListItem","position":2,"name":"B. Two Fairs \u89e3\u6790(\u601d\u7dad\u3001DFS\u3001\u7d44\u5408)"}]},{"@type":"WebSite","@id":"https:\/\/blog.seekrealthing.net\/blog\/#website","url":"https:\/\/blog.seekrealthing.net\/blog\/","name":"Logic Formatting","description":"","publisher":{"@id":"https:\/\/blog.seekrealthing.net\/blog\/#organization"},"potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/blog.seekrealthing.net\/blog\/?s={search_term_string}"},"query-input":{"@type":"PropertyValueSpecification","valueRequired":true,"valueName":"search_term_string"}}],"inLanguage":"zh-TW"},{"@type":"Organization","@id":"https:\/\/blog.seekrealthing.net\/blog\/#organization","name":"Logic Formatting","url":"https:\/\/blog.seekrealthing.net\/blog\/","logo":{"@type":"ImageObject","inLanguage":"zh-TW","@id":"https:\/\/blog.seekrealthing.net\/blog\/#\/schema\/logo\/image\/","url":"https:\/\/blog.seekrealthing.net\/blog\/wp-content\/uploads\/2025\/02\/android-chrome-512x512-1.png","contentUrl":"https:\/\/blog.seekrealthing.net\/blog\/wp-content\/uploads\/2025\/02\/android-chrome-512x512-1.png","width":512,"height":512,"caption":"Logic Formatting"},"image":{"@id":"https:\/\/blog.seekrealthing.net\/blog\/#\/schema\/logo\/image\/"}},{"@type":"Person","@id":"https:\/\/blog.seekrealthing.net\/blog\/#\/schema\/person\/233e80a0fee3d4706f067f2e88c0b454","name":"jeff","image":{"@type":"ImageObject","inLanguage":"zh-TW","@id":"https:\/\/blog.seekrealthing.net\/blog\/#\/schema\/person\/image\/","url":"https:\/\/secure.gravatar.com\/avatar\/f9b571b28c252728386f0002b35d9cb9a9028f740b0f9ca5ad678e7eb21c4857?s=96&d=mm&r=g","contentUrl":"https:\/\/secure.gravatar.com\/avatar\/f9b571b28c252728386f0002b35d9cb9a9028f740b0f9ca5ad678e7eb21c4857?s=96&d=mm&r=g","caption":"jeff"},"sameAs":["http:\/\/150.230.63.147\/blog"],"url":"https:\/\/blog.seekrealthing.net\/blog\/?author=1"}]}},"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/blog.seekrealthing.net\/blog\/index.php?rest_route=\/wp\/v2\/posts\/49","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blog.seekrealthing.net\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.seekrealthing.net\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.seekrealthing.net\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.seekrealthing.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=49"}],"version-history":[{"count":1,"href":"https:\/\/blog.seekrealthing.net\/blog\/index.php?rest_route=\/wp\/v2\/posts\/49\/revisions"}],"predecessor-version":[{"id":50,"href":"https:\/\/blog.seekrealthing.net\/blog\/index.php?rest_route=\/wp\/v2\/posts\/49\/revisions\/50"}],"wp:attachment":[{"href":"https:\/\/blog.seekrealthing.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=49"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.seekrealthing.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=49"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.seekrealthing.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=49"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}