{"id":132,"date":"2010-09-10T09:56:25","date_gmt":"2010-09-10T09:56:25","guid":{"rendered":"65ded5353c5ee48d0b7d48c591b8f430"},"modified":"2010-09-10T09:56:25","modified_gmt":"2010-09-10T09:56:25","slug":"","status":"publish","type":"post","link":"https:\/\/www.xiaobo.li\/notes\/archives\/132","title":{"rendered":"\u6d77\u91cf\u6570\u636e\u4e4b\u54c8\u5e0c"},"content":{"rendered":"

 <\/p>\n

\u9002\u7528\u8303\u56f4\uff1a\u5feb\u901f\u67e5\u627e\uff0c\u5220\u9664\u7684\u57fa\u672c\u6570\u636e\u7ed3\u6784\uff0c\u901a\u5e38\u9700\u8981\u603b\u6570\u636e\u91cf\u53ef\u4ee5\u653e\u5165\u5185\u5b58 <\/span>
\n
\u57fa\u672c\u539f\u7406\u53ca\u8981\u70b9\uff1a <\/span>
\n
hash\u51fd\u6570\u9009\u62e9\uff0c\u9488\u5bf9\u5b57\u7b26\u4e32\uff0c\u6574\u6570\uff0c\u6392\u5217\uff0c\u5177\u4f53\u76f8\u5e94\u7684hash\u65b9\u6cd5\u3002 <\/span>
\n
\u78b0\u649e\u5904\u7406\uff0c\u4e00\u79cd\u662fopen hashing\uff0c\u4e5f\u79f0\u4e3a\u62c9\u94fe\u6cd5\uff1b\u53e6\u4e00\u79cd\u5c31\u662fclosed hashing\uff0c\u4e5f\u79f0\u5f00\u5730\u5740\u6cd5\uff0copened addressing\u3002<\/span>
\n<\/span>\n<\/p>\n

(1)\u5f00\u653e\u5b9a\u5740\u6cd5 <\/span>
\n
hi=(h(key)+di) mod m i=1,2,...,k(k<=m-1) <\/span>
\n
\u5176\u4e2dm\u4e3a\u8868\u957f\uff0cdi\u4e3a\u589e\u91cf\u5e8f\u5217 <\/span>
\n
\u5982\u679cdi\u503c\u53ef\u80fd\u4e3a1,2,3,...m-1\uff0c\u79f0\u7ebf\u6027\u63a2\u6d4b\u518d\u6563\u5217\u3002 <\/span>
\n
\u5982\u679cdi\u53d6\u503c\u53ef\u80fd\u4e3a1,-1,2,-2,4,-4,9,-9,16,-16,...k*k,-k*k(k<=m\/2) <\/span>
\n
\u79f0\u4e8c\u6b21\u63a2\u6d4b\u518d\u6563\u5217\u3002 <\/span>
\n
\u5982\u679cdi\u53d6\u503c\u53ef\u80fd\u4e3a\u4f2a\u968f\u673a\u6570\u5217\u3002\u79f0\u4f2a\u968f\u673a\u63a2\u6d4b\u518d\u6563\u5217\u3002\u5f00\u653e\u5730\u5740\u6cd5\u5806\u88c5\u586b\u56e0\u5b50\u7684\u8981\u6c42 <\/span>
\n
\u5f00\u653e\u5b9a\u5740\u6cd5\u8981\u6c42\u6563\u5217\u8868\u7684\u88c5\u586b\u56e0\u5b50α≤l\uff0c\u5b9e\u7528\u4e2d\u53d6α\u4e3a0.5\u52300.9\u4e4b\u95f4\u7684\u67d0\u4e2a\u503c\u4e3a\u5b9c\u3002<\/span>
\n<\/span>\n<\/p>\n

(2)\u4e8c\u6b21\u63a2\u67e5\u6cd5(quadratic probing) <\/span>
\n
\u4e8c\u6b21\u63a2\u67e5\u6cd5\u7684\u63a2\u67e5\u5e8f\u5217\u662f\uff1a <\/span>
\n
hi=(h(key)+i*i)\uff05m 0≤i≤m-1 \/\/\u5373di=i2 <\/span>
\n
\u5373\u63a2\u67e5\u5e8f\u5217\u4e3ad=h(key)\uff0cd+12\uff0cd+22\uff0c…\uff0c\u7b49\u3002 <\/span>
\n
\u8be5\u65b9\u6cd5\u7684\u7f3a\u9677\u662f\u4e0d\u6613\u63a2\u67e5\u5230\u6574\u4e2a\u6563\u5217\u7a7a\u95f4\u3002<\/span>
\n<\/span>\n<\/p>\n

(3)\u53cc\u91cd\u6563\u5217\u6cd5(double hashing) <\/span>
\n
\u8be5\u65b9\u6cd5\u662f\u5f00\u653e\u5b9a\u5740\u6cd5\u4e2d\u6700\u597d\u7684\u65b9\u6cd5\u4e4b\u4e00\uff0c\u5b83\u7684\u63a2\u67e5\u5e8f\u5217\u662f\uff1a <\/span>
\n
hi=(h(key)+i*h1(key))\uff05m 0≤i≤m-1 \/\/\u5373di=i*h1(key) <\/span>
\n
\u5373\u63a2\u67e5\u5e8f\u5217\u4e3a\uff1a <\/span>
\n
d=h(key)\uff0c(d+h1(key))\uff05m\uff0c(d+2h1(key))\uff05m\uff0c…\uff0c\u7b49\u3002 <\/span>
\n
\u8be5\u65b9\u6cd5\u4f7f\u7528\u4e86\u4e24\u4e2a\u6563\u5217\u51fd\u6570h(key)\u548ch1(key)\uff0c\u6545\u4e5f\u79f0\u4e3a\u53cc\u6563\u5217\u51fd\u6570\u63a2\u67e5\u6cd5\u3002<\/span>
\n<\/span>\n<\/p>\n

(4)\u62c9\u94fe\u6cd5 <\/span>
\n
\u62c9\u94fe\u6cd5\u89e3\u51b3\u51b2\u7a81\u7684\u505a\u6cd5\u662f\uff1a\u5c06\u6240\u6709\u5173\u952e\u5b57\u4e3a\u540c\u4e49\u8bcd\u7684\u7ed3\u70b9\u94fe\u63a5\u5728\u540c\u4e00\u4e2a\u5355\u94fe\u8868\u4e2d\u3002\u82e5\u9009\u5b9a\u7684\u6563\u5217\u8868\u957f\u5ea6\u4e3am\uff0c\u5219\u53ef\u5c06\u6563\u5217\u8868\u5b9a\u4e49\u4e3a\u4e00\u4e2a\u7531m\u4e2a\u5934\u6307\u9488\u7ec4\u6210\u7684\u6307\u9488\u6570\u7ec4t[0..m-1]\u3002\u51e1\u662f\u6563\u5217\u5730\u5740\u4e3ai\u7684\u7ed3\u70b9\uff0c\u5747\u63d2\u5165\u5230\u4ee5t\u4e3a\u5934\u6307\u9488\u7684\u5355\u94fe\u8868\u4e2d\u3002t\u4e2d\u5404\u5206\u91cf\u7684\u521d\u503c\u5747\u5e94\u4e3a\u7a7a\u6307\u9488\u3002\u5728\u62c9\u94fe\u6cd5\u4e2d\uff0c\u88c5\u586b\u56e0\u5b50α\u53ef\u4ee5\u5927\u4e8e1\uff0c\u4f46\u4e00\u822c\u5747\u53d6α≤1\u3002<\/span>
\n<\/span>\n<\/p>\n

(5)\u5efa\u7acb\u4e00\u4e2a\u516c\u5171\u6ea2\u51fa\u533a <\/span>
\n
\u5047\u8bbe\u54c8\u5e0c\u51fd\u6570\u7684\u503c\u57df\u4e3a[0,m-1],\u5219\u8bbe\u5411\u91cfhashtable[0..m-1]\u4e3a\u57fa\u672c\u8868\uff0c\u53e6\u5916\u8bbe\u7acb\u5b58\u50a8\u7a7a\u95f4\u5411\u91cfovertable[0..v]\u7528\u4ee5\u5b58\u50a8\u53d1\u751f\u51b2\u7a81\u7684\u8bb0\u5f55\u3002 <\/span>
\n

\u6269\u5c55\uff1a <\/span>
\n
d-left hashing<\/font>
\n\u4e2d\u7684d\u662f\u591a\u4e2a\u7684\u610f\u601d\uff0c\u6211\u4eec\u5148\u7b80\u5316\u8fd9\u4e2a\u95ee\u9898\uff0c\u770b\u4e00\u770b2-left hashing\u30022-left hashing\u6307\u7684\u662f\u5c06\u4e00\u4e2a\u54c8\u5e0c\u8868\u5206\u6210\u957f\u5ea6\u76f8\u7b49\u7684\u4e24\u534a\uff0c\u5206\u522b\u53eb\u505aT1\u548cT2\uff0c\u7ed9T1\u548cT2\u5206\u522b\u914d\u5907\u4e00\u4e2a\u54c8\u5e0c\u51fd\u6570\uff0ch1\u548ch2\u3002\u5728\u5b58\u50a8\u4e00\u4e2a\u65b0\u7684key\u65f6\uff0c\u540c \u65f6\u7528\u4e24\u4e2a\u54c8\u5e0c\u51fd\u6570\u8fdb\u884c\u8ba1\u7b97\uff0c\u5f97\u51fa\u4e24\u4e2a\u5730\u5740h1[key]\u548ch2[key]\u3002\u8fd9\u65f6\u9700\u8981\u68c0\u67e5T1\u4e2d\u7684h1[key]\u4f4d\u7f6e\u548cT2\u4e2d\u7684h2[key]\u4f4d\u7f6e\uff0c\u54ea\u4e00\u4e2a \u4f4d\u7f6e\u5df2\u7ecf\u5b58\u50a8\u7684\uff08\u6709\u78b0\u649e\u7684\uff09key\u6bd4\u8f83\u591a\uff0c\u7136\u540e\u5c06\u65b0key\u5b58\u50a8\u5728\u8d1f\u8f7d\u5c11\u7684\u4f4d\u7f6e\u3002\u5982\u679c\u4e24\u8fb9\u4e00\u6837\u591a\uff0c\u6bd4\u5982\u4e24\u4e2a\u4f4d\u7f6e\u90fd\u4e3a\u7a7a\u6216\u8005\u90fd\u5b58\u50a8\u4e86\u4e00\u4e2akey\uff0c\u5c31\u628a\u65b0key \u5b58\u50a8\u5728\u5de6\u8fb9\u7684T1\u5b50\u8868\u4e2d\uff0c2-left\u4e5f\u7531\u6b64\u800c\u6765\u3002\u5728\u67e5\u627e\u4e00\u4e2akey\u65f6\uff0c\u5fc5\u987b\u8fdb\u884c\u4e24\u6b21hash\uff0c\u540c\u65f6\u67e5\u627e\u4e24\u4e2a\u4f4d\u7f6e\u3002 <\/span>
\n

\u95ee\u9898\u5b9e\u4f8b\uff1a <\/span>
\n
1).\u6d77\u91cf\u65e5\u5fd7\u6570\u636e\uff0c\u63d0\u53d6\u51fa\u67d0\u65e5\u8bbf\u95ee\u767e\u5ea6\u6b21\u6570\u6700\u591a\u7684\u90a3\u4e2aIP\u3002 <\/span>
\n

IP\u7684\u6570\u76ee\u8fd8\u662f\u6709\u9650\u7684\uff0c\u6700\u591a2^32\u4e2a\uff0c\u6240\u4ee5\u53ef\u4ee5\u8003\u8651\u4f7f\u7528hash\u5c06ip\u76f4\u63a5\u5b58\u5165\u5185\u5b58\uff0c\u7136\u540e\u8fdb\u884c\u7edf\u8ba1\u3002<\/span>
\n<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

 <\/p>\n

\u9002\u7528\u8303\u56f4\uff1a\u5feb\u901f\u67e5\u627e\uff0c\u5220\u9664\u7684\u57fa\u672c\u6570\u636e\u7ed3\u6784\uff0c\u901a\u5e38\u9700\u8981\u603b\u6570\u636e\u91cf\u53ef\u4ee5\u653e\u5165\u5185\u5b58
\u57fa\u672c\u539f\u7406\u53ca\u8981\u70b9\uff1a
hash\u51fd\u6570\u9009\u62e9\uff0c\u9488\u5bf9\u5b57\u7b26\u4e32\uff0c\u6574\u6570\uff0c\u6392\u5217\uff0c\u5177\u4f53\u76f8\u5e94\u7684hash\u65b9\u6cd5\u3002
\u78b0\u649e\u5904\u7406\uff0c\u4e00\u79cd\u662fopen hashing\uff0c\u4e5f\u79f0\u4e3a\u62c9\u94fe\u6cd5\uff1b\u53e6\u4e00\u79cd\u5c31\u662fclosed hashing\uff0c\u4e5f\u79f0\u5f00\u5730\u5740\u6cd5\uff0copened addressing\u3002<\/span><\/span><\/p>\n

(1)\u5f00\u653e\u5b9a\u5740\u6cd5
hi=(h(key)+di) mod m i=1,2,...,k(k<=m-1)
\u5176\u4e2dm\u4e3a\u8868\u957f\uff0cdi\u4e3a\u589e\u91cf\u5e8f\u5217
\u5982\u679cdi\u503c\u53ef\u80fd\u4e3a1,2,3,...m-1\uff0c\u79f0\u7ebf\u6027\u63a2\u6d4b\u518d\u6563\u5217\u3002
\u5982\u679cdi\u53d6\u503c\u53ef\u80fd\u4e3a1,-1,2,-2,4,-4,9,-9,16,-16,...k*k,-k*k(k<=m\/2)
\u79f0\u4e8c\u6b21\u63a2\u6d4b\u518d\u6563\u5217\u3002
\u5982\u679cdi\u53d6\u503c\u53ef\u80fd\u4e3a\u4f2a\u968f\u673a\u6570\u5217\u3002\u79f0\u4f2a\u968f\u673a\u63a2\u6d4b\u518d\u6563\u5217\u3002\u5f00\u653e\u5730\u5740\u6cd5\u5806\u88c5\u586b\u56e0\u5b50\u7684\u8981\u6c42
\u5f00\u653e\u5b9a\u5740\u6cd5\u8981\u6c42\u6563\u5217\u8868\u7684\u88c5\u586b\u56e0\u5b50α≤l\uff0c\u5b9e\u7528\u4e2d\u53d6α\u4e3a0.5\u52300.9\u4e4b\u95f4\u7684\u67d0\u4e2a\u503c\u4e3a\u5b9c\u3002<\/span><\/span><\/p>\n

(2)\u4e8c\u6b21\u63a2\u67e5\u6cd5(quadratic probing)
\u4e8c\u6b21\u63a2\u67e5\u6cd5\u7684\u63a2\u67e5\u5e8f\u5217\u662f\uff1a
hi=(h(key)+i*i)\uff05m 0≤i≤m-1 \/\/\u5373di=i2
\u5373\u63a2\u67e5\u5e8f\u5217\u4e3ad=h(k...<\/span><\/span><\/p>\n

\u7ee7\u7eed\u9605\u8bfb →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[273],"tags":[51],"class_list":["post-132","post","type-post","status-publish","format-standard","hentry","category-article","tag-DB"],"_links":{"self":[{"href":"https:\/\/www.xiaobo.li\/notes\/wp-json\/wp\/v2\/posts\/132","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.xiaobo.li\/notes\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.xiaobo.li\/notes\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.xiaobo.li\/notes\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.xiaobo.li\/notes\/wp-json\/wp\/v2\/comments?post=132"}],"version-history":[{"count":0,"href":"https:\/\/www.xiaobo.li\/notes\/wp-json\/wp\/v2\/posts\/132\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.xiaobo.li\/notes\/wp-json\/wp\/v2\/media?parent=132"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.xiaobo.li\/notes\/wp-json\/wp\/v2\/categories?post=132"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.xiaobo.li\/notes\/wp-json\/wp\/v2\/tags?post=132"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}