{"id":7415,"date":"2026-07-22T00:14:54","date_gmt":"2026-07-21T16:14:54","guid":{"rendered":"https:\/\/i007.cc\/wordpress\/?p=7415"},"modified":"2026-07-22T00:14:54","modified_gmt":"2026-07-21T16:14:54","slug":"%e5%a6%82%e4%bd%95%e7%94%a8c%e8%ae%be%e8%ae%a1lru-lfu-%e7%bc%93%e5%ad%98","status":"publish","type":"post","link":"https:\/\/i007.cc\/wordpress\/archives\/7415","title":{"rendered":"\u5982\u4f55\u7528C++\u8bbe\u8ba1LRU \/ LFU \u7f13\u5b58"},"content":{"rendered":"

C++ \u8bbe\u8ba1\u8981\u70b9\u8be6\u89e3<\/h3>\n

\u4e00\u3001LRU \u2014\u2014 std::list<\/code> + std::unordered_map<K, list::iterator><\/code><\/h4>\n

C++ \u7684\u6838\u5fc3\u6280\u5de7\u662f\u628a list \u7684\u8fed\u4ee3\u5668\u5b58\u8fdb map<\/strong>\uff0c\u800c\u4e0d\u662f\u5b58\u503c\u672c\u8eab\u3002<\/p>\n

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cpp<\/div>\n
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std::list<std::pair<K,V>>                           list_;\r\nstd::unordered_map<K, list<pair<K,V>>::iterator>    map_;<\/pre>\n
 <\/p>\n<\/div>\n<\/div>\n
\u8fd9\u91cc\u6709\u4e24\u4e2a\u5173\u952e\u6027\u8d28\uff1a<\/p>\n
list::splice<\/code> \u662f O(1) \u4e14\u8fed\u4ee3\u5668\u4e0d\u5931\u6548\u3002<\/strong> \u628a\u8282\u70b9\u4ece\u5f53\u524d\u4f4d\u7f6e\u79fb\u5230\u94fe\u8868\u5934\u53ea\u9700\u8981\u4fee\u6539\u4e09\u5bf9\u6307\u9488\uff0cmap \u91cc\u5b58\u7684\u8fed\u4ee3\u5668\u6839\u672c\u4e0d\u9700\u8981\u66f4\u65b0\uff0c\u8fd9\u662f\u548c Python \u7248\u624b\u5199\u94fe\u8868\u622a\u7136\u4e0d\u540c\u7684\u5730\u65b9\u3002<\/p>\n
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cpp<\/div>\n
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\/\/ \u628a it \u6240\u6307\u8282\u70b9\u79fb\u5230\u94fe\u8868\u5934\uff0cO(1)\uff0cit \u4f9d\u7136\u6709\u6548\r\nlist_.splice(list_.begin(), list_, it->second);<\/pre>\n
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\u6dd8\u6c70\u65f6\u8282\u70b9\u91cc\u5fc5\u987b\u5b58 key<\/strong>\uff0c\u56e0\u4e3a\u4ece list.back()<\/code> \u62ff\u5230\u6dd8\u6c70\u8282\u70b9\u540e\u9700\u8981\u7acb\u5373\u53bb map \u91cc erase(key)<\/code>\uff0c\u5982\u679c\u53ea\u5b58 value \u5c31\u627e\u4e0d\u5230 key \u4e86\u3002<\/p>\n
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cpp<\/div>\n
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if ((int)map_.size() == cap_) {\r\n    auto& lru = list_.back();   \/\/ pair<K,V>\r\n    map_.erase(lru.first);      \/\/ \u7528 key \u5220 map\r\n    list_.pop_back();\r\n}<\/pre>\n
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\u4e8c\u3001LFU \u2014\u2014 \u53cc unordered_map<\/code> + \u9891\u7387\u6876\u94fe\u8868<\/h4>\n
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cpp<\/div>\n
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std::unordered_map<K, NodeIter>     key_map_;   \/\/ key \u2192 \u94fe\u8868\u8fed\u4ee3\u5668\r\nstd::unordered_map<int, NodeList>   freq_map_;  \/\/ freq \u2192 \u6309\u8bbf\u95ee\u987a\u5e8f\u7684\u94fe\u8868\r\nint min_freq_;<\/pre>\n
 <\/p>\n<\/div>\n<\/div>\n
Node \u91cc\u5fc5\u987b\u540c\u65f6\u5b58 key<\/code> \u548c freq<\/code>\uff0c\u539f\u56e0\u548c LRU \u7c7b\u4f3c\uff1a\u6dd8\u6c70\u65f6\u8981\u62ff key \u53bb key_map_<\/code> \u91cc\u5220\uff0c\u9891\u7387\u53d8\u5316\u65f6\u8981\u77e5\u9053\u4ece\u54ea\u4e2a\u6876\u8fc1\u51fa\u3002<\/p>\n
_bump_freq<\/code> \u662f\u6574\u4e2a LFU \u7684\u6838\u5fc3<\/strong>\uff0c\u540c\u6837\u5229\u7528 splice<\/code> \u505a\u5230 O(1)\uff1a<\/p>\n
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void _bump_freq(NodeIter node_it) {\r\n    int old_freq = node_it->freq;\r\n    node_it->freq++;\r\n    freq_map_[node_it->freq].splice(\r\n        freq_map_[node_it->freq].end(),\r\n        freq_map_[old_freq],\r\n        node_it                          \/\/ \u8fed\u4ee3\u5668\u8fc1\u79fb\u540e\u4f9d\u7136\u6709\u6548\r\n    );\r\n    if (freq_map_[old_freq].empty() && old_freq == min_freq_)\r\n        min_freq_++;\r\n}<\/pre>\n
 <\/p>\n<\/div>\n<\/div>\n
min_freq<\/code> \u7684\u7ef4\u62a4\u89c4\u5219\u53ea\u6709\u4e24\u6761\uff1aput \u65b0\u8282\u70b9\u65f6\u7f6e 1\uff1b\u65e7\u6876\u53d8\u7a7a\u4e14\u7b49\u4e8e min_freq<\/code> \u65f6 +1\u3002\u4e0d\u80fd\u8df3\u8dc3\uff0c\u56e0\u4e3a\u9891\u7387\u53ea\u80fd\u9010\u6b65\u589e\u957f\u3002<\/p>\n
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\u4e09\u3001C++ vs Python \u5b9e\u73b0\u7684\u5173\u952e\u5dee\u5f02<\/h4>\n
\n\n\n\n\n\n\n\n\n\n
\u7ef4\u5ea6<\/th>\nPython<\/th>\nC++<\/th>\n<\/tr>\n<\/thead>\n
\u53cc\u5411\u94fe\u8868<\/td>\n\u624b\u5199 Node<\/code> + \u54e8\u5175<\/td>\nstd::list<\/code>\uff08\u6807\u51c6\u5e93\u81ea\u5e26\uff09<\/td>\n<\/tr>\n
\u8282\u70b9\u79fb\u52a8<\/td>\n\u624b\u52a8\u6458\u94fe + \u63d2\u5165\uff0cO(1)<\/td>\nlist::splice<\/code>\uff0cO(1)\uff0c\u8fed\u4ee3\u5668\u4e0d\u5931\u6548<\/td>\n<\/tr>\n
\u54c8\u5e0c\u8868\u503c<\/td>\n\u8282\u70b9\u6307\u9488<\/td>\nlist::iterator<\/code>\uff08\u672c\u8d28\u4e5f\u662f\u6307\u9488\u5305\u88c5\uff09<\/td>\n<\/tr>\n
\u6a21\u677f\u5316<\/td>\nOrderedDict<\/code> \u5929\u7136\u6cdb\u578b<\/td>\ntemplate <typename K, typename V><\/code><\/td>\n<\/tr>\n
\u5185\u5b58<\/td>\nGC \u81ea\u52a8\u56de\u6536<\/td>\nlist.erase<\/code> \/ pop_back<\/code> \u7acb\u5373\u91ca\u653e<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n
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\u56db\u3001\u5de5\u7a0b\u6269\u5c55\u65b9\u5411<\/h4>\n
\u7ebf\u7a0b\u5b89\u5168<\/strong>\uff1a\u5728 get\/put<\/code> \u5916\u5c42\u52a0 std::shared_mutex<\/code>\uff0c\u8bfb\u64cd\u4f5c\u7528 shared_lock<\/code>\uff0c\u5199\u64cd\u4f5c\u7528 unique_lock<\/code>\u3002\u4f46\u6ce8\u610f LRU \u7684 get<\/code> \u4e5f\u4f1a\u4fee\u6539\u94fe\u8868\u987a\u5e8f\uff0c\u6240\u4ee5 get<\/code> \u4e5f\u9700\u8981 unique_lock<\/code>\uff0c\u9664\u975e\u63a5\u53d7\u8fd1\u4f3c LRU \u8bed\u4e49\u3002<\/p>\n
\u8fc7\u671f\u65f6\u95f4\uff08TTL\uff09<\/strong>\uff1aNode \u91cc\u52a0 std::chrono::steady_clock::time_point expire<\/code>\uff0cget \u65f6\u68c0\u67e5\u662f\u5426\u8fc7\u671f\uff0c\u8fc7\u671f\u89c6\u4e3a miss \u5e76\u5220\u9664\u3002<\/p>\n
\u5bb9\u91cf\u7edf\u8ba1<\/strong>\uff1a\u5982\u679c value \u662f\u53d8\u957f\u6570\u636e\uff08\u5982\u5b57\u8282\u4e32\uff09\uff0c\u53ef\u4ee5\u6539\u4e3a\u6309\u5b57\u8282\u6570\u9650\u5bb9\uff0cput<\/code> \u65f6\u5faa\u73af\u6dd8\u6c70\u76f4\u5230\u5269\u4f59\u5bb9\u91cf\u8db3\u591f\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
C++ \u8bbe\u8ba1\u8981\u70b9\u8be6\u89e3 \u4e00\u3001LRU \u2014\u2014 <\/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":[24],"tags":[],"class_list":["post-7415","post","type-post","status-publish","format-standard","hentry","category-value_docs"],"_links":{"self":[{"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/posts\/7415","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=7415"}],"version-history":[{"count":1,"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/posts\/7415\/revisions"}],"predecessor-version":[{"id":7416,"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/posts\/7415\/revisions\/7416"}],"wp:attachment":[{"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/media?parent=7415"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/categories?post=7415"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/tags?post=7415"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}