{"id":1531,"date":"2018-07-20T20:45:44","date_gmt":"2018-07-20T12:45:44","guid":{"rendered":"https:\/\/damogame.cn:15443\/wordpress\/?p=1531"},"modified":"2018-07-20T20:45:44","modified_gmt":"2018-07-20T12:45:44","slug":"%e5%85%b3%e4%ba%8emap%e5%92%8cunordered_map%e8%bf%98%e9%9c%80%e8%a6%81%e7%9f%a5%e9%81%93%e7%9a%84","status":"publish","type":"post","link":"https:\/\/i007.cc\/wordpress\/archives\/1531","title":{"rendered":"\u5173\u4e8emap\u548cunordered_map\u8fd8\u9700\u8981\u77e5\u9053\u7684"},"content":{"rendered":"

\u5173\u4e8emap\u548cunordered_map\u8fd8\u9700\u8981\u77e5\u9053\u7684<\/h1>\n
\"96\"<\/a><\/p>\n
lxfeng<\/a><\/span>\u00a0<\/i>\u5173\u6ce8<\/a><\/p>\n
2016.06.18 21:57*<\/span>\u00a0\u5b57\u6570 683<\/span>\u00a0\u9605\u8bfb 1089<\/span>\u8bc4\u8bba 0<\/span>\u559c\u6b22 3<\/span><\/div>\n<\/div>\n<\/div>\n
\n
\n
\n

\u6700\u8fd1\u5728\u4f7f\u7528unordered_map\u7684\u65f6\u5019\u9047\u5230\u51e0\u4e2a\u95ee\u9898\uff0c\u5728\u6b64\u8bb0\u5f55\u4e0b\uff0c\u9879\u76ee\u4e2d\u7528\u6237\u753b\u50cf\u6570\u636e\u672c\u6765\u7684\u5b58\u50a8\u65b9\u5f0f\u662fmap\uff0c\u56e0\u4e3a\u903b\u8f91\u4e2d\u9700\u8981\u6bcf\u6b21\u8bf7\u6c42\uff0c\u6839\u636eid\u53d6value\u3002\u6d4b\u8bd5\u65f6\uff0c\u5f53\u65f6\u865a\u62df\u673a\u91cc\u8dd1\uff0c\u6bcf\u6b21\u8bf7\u6c42\u8ba1\u7b97\u8fc7\u7a0b\u9700\u8981200\u591ams\uff0c\u8fd9\u4e2a\u6027\u80fd\u662f\u4e0d\u80fd\u63a5\u53d7\uff0c\u6211\u4ee5\u4e3a\u662f\u4ee3\u7801\u6027\u80fd\u95ee\u9898\u3002\u53bb\u5c1d\u8bd5\u7528unordered_map\u5b58\u50a8\uff0c\u4f46\u9047\u5230\u4e86\u51e0\u4e2a\u95ee\u9898\u3002\u540e\u6765\u53d1\u73b0\u662f\u5f53\u65f6window\u597d\u4e45\u53ef\u80fd\u597d\u4e45\u6ca1\u5173\u673a\uff0c\u7cfb\u7edf\u7565\u5361\uff0c\u5bfc\u81f4\u865a\u62df\u673a\u4e5f\u5361\u3002<\/p>\n

1.unordered_map\u7684\u67e5\u627e\u771f\u7684\u5f88\u5feb\u5417\uff1f<\/h3>\n

map\u672c\u8d28\u662f\u4e00\u4e2a\u4e8c\u53c9\u6811\uff0c\u4e8c\u53c9\u6811\u7684\u6bcf\u6b21\u67e5\u627e\u662fO(lgN),\u54c8\u5e0c\u8868\u7684\u67e5\u627e\u53ea\u662f\u505a\u4e00\u4e2ahash\u8ba1\u7b97\uff0c\u7136\u540e\u6839\u636eid\u8bbf\u95ee\u5143\u7d20\uff0c\u6240\u4ee5\u5b83\u7684\u67e5\u627e\u662f\u4e00\u4e2aO(1).\u6240\u4ee5\u9700\u8981\u9891\u7e41\u67e5\u627e\u7684\u4f7f\u7528unordered_map\u4f1a\u63d0\u5347\u6027\u80fd\uff0c\u6211\u628a\u4e0a\u8ff0\u6539\u4e3aunordered_map\u4e86\uff0c\u4f46\u662f\u6d4b\u8bd5\u7ed3\u679c\u6548\u7387\u6ca1\u6709\u5347\u53cd\u800c\u964d\u4e86\u3002\u6211\u6d4b\u8bd5\u4e86\u5982\u4e0b\u4ee3\u7801\uff1a<\/p>\n

while<\/span> (i < m) {\r\n    map<\/span>[i] = i + 1<\/span>;\r\n    umap[i] = i + 1<\/span>;\r\n    i++;\r\n}\r\nwhile<\/span>(i < n) {\r\n    map<\/span>.find(5<\/span>);\r\n    i++;\r\n}\r\nwhile<\/span> (i < n) {\r\n    umap.find(1399<\/span>);\r\n    i++;\r\n}\r\n<\/code><\/pre>\n
\u5728m=10, n=100000\u65f6\uff1a<\/p>\n
unordered_map<\/span> cost: 8032<\/span>\r\nmap<\/span> cost :6852<\/span>\r\n<\/code><\/pre>\n
\u5728m=100, n=100000\u65f6\uff1a<\/p>\n
unordered_map<\/span> cost: 8572<\/span>\r\nmap<\/span> cost :10844<\/span>\r\n<\/code><\/pre>\n
\u6211\u4eec\u77e5\u9053hashmap\u662f\u5e73\u5747O(1),map\u662f\u5e73\u5747O(lnN)\u7684\uff0c\u5b9e\u8df5\u4e0a\u5e76\u4e0d\u603b\u662f\u5982\u6b64\uff0c\u6709\u4e00\u4e0b\u51e0\u70b9\u9700\u8981\u8003\u8651\uff1a<\/p>\n
    \n
  • hashmap\u7684hash\u7b97\u6cd5\u662f\u4e0d\u662f\u9700\u8981\u7ecf\u8fc7\u590d\u6742\u7684\u8ba1\u7b97\u3002<\/li>\n
  • \u78b0\u649e\u7684\u6b21\u6570
    \n\u4e00\u822c\u5728\u6570\u636e\u91cf\u5c0f\u7684\u60c5\u51b5\u4e0b\uff0cunordered_map\u7684\u6027\u80fd\u4e0d\u5982map\u7684\u3002<\/li>\n<\/ul>\n
    2.unordered_map\u7684\u521d\u59cb\u5316<\/h3>\n
    \u5728\u4ee3\u7801\u4e2d.h\u4e2d\u5b9a\u4e49\u4e86\u4e00\u4e2aFeature\u7ed3\u6784\u4f53\uff1a<\/p>\n
    struct<\/span> Feature<\/span> {<\/span>\r\n    std<\/span>::unordered_map<\/span><int<\/span>, int<\/span>> price;\r\n    std<\/span>::unordered_map<\/span><int<\/span>, int<\/span>> brand;\r\n    std<\/span>::unordered_map<\/span><int<\/span>, int<\/span>> seller;\r\n}\r\n<\/code><\/pre>\n
    \u66ff\u6362\u539f\u6765\u7684map\u540e\u6765\uff0c\u53d1\u73b0\u6027\u80fd\u4e0d\u5347\u53cd\u964d\uff0c\u5c31\u6ce8\u6389.cc\u4e2d\u7684\u4ee3\u7801\uff0c\u4f46\u58f0\u660e\u5c40\u90e8\u53d8\u91cf\u90a3\u53e5\u5fd8\u4e86\u6ce8\u6389\u3002\u6ce8\u6389\u540e\u53d1\u73b0\uff0c\u6027\u80fd\u8fd8\u662f\u6ca1\u6709\u6062\u590d\u5230\u4fee\u6539\u524d\u7684\u3002\u6700\u540e\u53d1\u73b0\u6ce8\u6389\u8fd9\u4e00\u53e5\u540e\uff0c\u6027\u80fd\u6062\u590d\u4e86\u3002\u6211\u5f53\u65f6\u7684\u611f\u89c9\u662f\uff0c\u8fd9\u53ea\u662f\u4e00\u4e2a\u5c40\u90e8\u53d8\u91cf\u800c\u4e14\u8fd8\u6ca1\u4f7f\u7528\u7684\uff0c\u51fd\u6570\u6267\u884c\u5b8c\u5e94\u8be5\u5c31\u91ca\u653e\u4e86\u3002\u4e3a\u5565\u8fd9\u4e48\u5f71\u54cd\u6027\u80fd\uff0c\u7136\u540e\u6211\u5199\u4e86\u4e2a\u6d4b\u8bd5\u4ee3\u7801\uff1a<\/p>\n
    auto<\/span> start = clock();                                                         \r\n  while<\/span> (i < 10000<\/span>) {\r\n    std<\/span>::unordered_map<\/span><int<\/span>, int<\/span>> umap;\r\n    ++i;\r\n  }\r\n  auto<\/span> end = clock();\r\n   \r\n  std<\/span>::cout<\/span> << \"unordered_map cost: \"<\/span> << end - start << std<\/span>::endl<\/span>;\r\n  i = 0<\/span>;\r\n  start = clock();\r\n  while<\/span> (i < 10000<\/span>) {\r\n    std<\/span>::map<\/span><int<\/span>, int<\/span>> map<\/span>;\r\n    ++i;\r\n  }\r\n  end = clock();\r\n   \r\n  std<\/span>::cout<\/span><< \"map cost :\"<\/span> <<end - start << std<\/span>::endl<\/span>;\r\n<\/code><\/pre>\n
    \u8fd0\u884c\u7ed3\u679c\uff1a<\/p>\n
    unordered_map<\/span> cost: 1994<\/span>\r\nmap<\/span> cost :423<\/span>\r\n<\/code><\/pre>\n
    \u7684\u786e\u662funordered_map\u7684\u521d\u59cb\u5316\u6bd4\u8f83\u8017\u65f6\uff0c\u6211\u4eec\u90fd\u77e5\u9053map\u662f\u7ea2\u9ed1\u6811\uff0cunordered_map\u662f\u54c8\u5e0c\u8868\uff0c\u9020\u6210\u6027\u80fd\u5dee\u5f02\u7684\u539f\u56e0\u5728\u4e8e\uff0c\u7ea2\u9ed1\u6811\u521d\u59cb\u5316\u65f6\uff0c\u8282\u70b9\u53ea\u9700\u8981\u4e00\u4e2a\uff0c\u540e\u7eed\u7684\u63d2\u5165\u53ea\u662f\u63d2\u5165\u65b0\u7684\u8282\u70b9\uff0c\u4f46\u662f\u54c8\u5e0c\u8868\u521d\u59cb\u5316\u65f6\u5c31\u4e0d\u662f\u90a3\u4e48\u7b80\u5355\u4e86\uff0c\u54c8\u5e0c\u8868\u521d\u59cb\u5316\u65f6\u9700\u8981\u7533\u8bf7\u4e00\u4e2a\u6570\u7ec4\uff0c\u6570\u7ec4\u7684\u6bcf\u4e2a\u5143\u7d20\u90fd\u6307\u5411\u4e00\u6761\u94fe\u8868\uff0c\u6240\u4ee5\u521d\u59cb\u5316\u65f6\u9700\u8981\u7533\u8bf7\u5f88\u591a\u5185\u5b58\uff0c\u76f8\u6bd4\u4e8emap\uff0c\u7684\u786e\u66f4\u8017\u65f6\u3002<\/p>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"
    \u5173\u4e8emap\u548cunordered_map\u8fd8<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"colormag_page_container_layout":"default_layout","colormag_page_sidebar_layout":"default_layout","footnotes":""},"categories":[],"tags":[118],"class_list":["post-1531","post","type-post","status-publish","format-standard","hentry","tag-02-"],"_links":{"self":[{"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/posts\/1531","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/comments?post=1531"}],"version-history":[{"count":0,"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/posts\/1531\/revisions"}],"wp:attachment":[{"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/media?parent=1531"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/categories?post=1531"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/tags?post=1531"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}