{"id":233,"date":"2012-05-26T18:28:56","date_gmt":"2012-05-26T10:28:56","guid":{"rendered":"http:\/\/www.shuizilong.com\/house\/?p=233"},"modified":"2012-05-26T18:28:56","modified_gmt":"2012-05-26T10:28:56","slug":"poj-2420-a-star-not-a-tree","status":"publish","type":"post","link":"https:\/\/www.shuizilong.com\/house\/archives\/poj-2420-a-star-not-a-tree\/","title":{"rendered":"POJ 2420. A Star not a Tree?"},"content":{"rendered":"<h3>Brief description : <\/h3>\n<p>\u3002\u5e7f\u4e49\u8d39\u9a6c\u70b9\u3002\u3002\uff09<\/p>\n<p><!--more--><\/p>\n<h3>Analysis :<\/h3>\n<p>\u3002\u3002\u7565\u3002\u3002\uff08\u3002\u3002\u8fd9\u4e2a\u9898\u53ef\u4ee5\u5411\u5f88\u591a\u65b9\u5411\u63a8\u5e7f\u3002\u3002\u4e00\u4e2a\u6bd4\u8f83\u96be\u7684\u65b9\u5411\u662f\u5141\u8bb8\u653e\u7f6e\u591a\u4e2a hub \u3002\u3002\u3002<\/p>\n<pre class=\"brush: cpp; collapse: true; first-line: 1; light: false; title: example-filename.cpp; toolbar: true; notranslate\" title=\"example-filename.cpp\">\r\nconst int I = 1, L = 100, W = 65536;\r\nconst DB V = 0.9;\r\n\r\n\/\/ I: \u521d\u59cb\u70b9\u6570\r\n\/\/ L: \u8fed\u4ee3\u6b21\u6570\r\n\/\/ V: \u964d\u706b\u901f\u7387\u3002\u3002\r\n\r\nconst int N = 109, C = 10000;\r\nPo P&#x5B;N]; int X, Y; Po res; DB ans;\r\nint n;\r\n\r\nbool check(Po p){\r\n    return p.x &gt;= 0 &amp;&amp; p.y &gt;= 0 &amp;&amp; p.x &lt;= C &amp;&amp; p.y &lt;= C;\r\n}\r\n\r\nDB f(Po p){\r\n    DB res = 0; REP(i, n) res += dist(P&#x5B;i], p);\r\n    return res;\r\n}\r\n\r\nvoid SA(){\r\n\r\n    ans = OO; DO_C(I){\r\n\r\n        Po cur = Po(C \/ 2, C \/ 2);\r\n        DB T = C \/ 2, best = f(cur);\r\n\r\n        while (T &gt; EPS){\r\n\r\n            bool improved = false;\r\n\r\n            Po pre = cur; DO_C(L){\r\n                DB theta = (DB) (rand() % W) \/ W * (2*PI);\r\n                Po suc = pre + Po(cos(theta), sin(theta)) * T;\r\n                DB temp = f(suc);\r\n                if (temp &lt; best){\r\n                    improved = true;\r\n                    best = temp, cur = suc;\r\n                }\r\n            }\r\n\r\n            if (!improved) T *= V;\r\n        }\r\n\r\n        if (best &lt; ans){\r\n            ans = best, res = cur;\r\n        }\r\n    }\r\n}\r\n\r\nint main(){\r\n\r\n#ifdef LOCAL\r\n    freopen(&quot;in.txt&quot;, &quot;r&quot;, stdin);\r\n#endif\r\n\r\n    while (scanf(&quot;%d&quot;, &amp;n) != EOF &amp;&amp; n){\r\n        REP(i, n) P&#x5B;i].input();\r\n        SA(); OT(ans);\r\n    }\r\n}\r\n<\/pre>\n<h3>External link: <\/h3>\n<p><a href=\"http:\/\/poj.org\/problem?id=2420\">http:\/\/poj.org\/problem?id=2420<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Brief description : \u3002\u5e7f\u4e49\u8d39\u9a6c\u70b9\u3002\u3002\uff09<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_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}}},"categories":[19],"tags":[72],"class_list":["post-233","post","type-post","status-publish","format-standard","hentry","category-poj","tag-72"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/p2tdP7-3L","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.shuizilong.com\/house\/wp-json\/wp\/v2\/posts\/233","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.shuizilong.com\/house\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.shuizilong.com\/house\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.shuizilong.com\/house\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.shuizilong.com\/house\/wp-json\/wp\/v2\/comments?post=233"}],"version-history":[{"count":0,"href":"https:\/\/www.shuizilong.com\/house\/wp-json\/wp\/v2\/posts\/233\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.shuizilong.com\/house\/wp-json\/wp\/v2\/media?parent=233"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.shuizilong.com\/house\/wp-json\/wp\/v2\/categories?post=233"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.shuizilong.com\/house\/wp-json\/wp\/v2\/tags?post=233"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}