{"id":4980,"date":"2020-04-19T17:13:53","date_gmt":"2020-04-19T09:13:53","guid":{"rendered":"https:\/\/www.xttblog.com\/?p=4980"},"modified":"2020-04-19T17:13:53","modified_gmt":"2020-04-19T09:13:53","slug":"java%e4%b8%ad%e7%9a%84%e8%ae%b0%e5%bf%86memoization%e7%ae%97%e6%b3%95","status":"publish","type":"post","link":"https:\/\/www.xttblog.com\/?p=4980","title":{"rendered":"Java\u4e2d\u7684\u8bb0\u5fc6(Memoization)\u7b97\u6cd5"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\">Memoization \u88ab\u5f88\u591a\u4eba\u7ffb\u8bd1\u6210\u8bb0\u5fc6\uff0c\u662f\u6839\u636e\u5b57\u9762\u610f\u601d\u6765\u7ffb\u8bd1\u7684\u3002\u4eca\u5929\u6211\u5c31\u6765\u8bf4\u4e00\u8bf4\u8bb0\u5fc6\u5316\u7b97\u6cd5\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u5b83\u5176\u5b9e\u662f\u4e00\u79cd\u5f88\u5de7\u5999\u7684\u601d\u60f3\u6216\u8bbe\u8ba1\uff0c\u88ab\u79f0\u4e3a\u7b97\u6cd5\uff0c\u6211\u60f3\u4e3b\u8981\u662f\u56e0\u4e3a\u5b83\u7ecf\u5e38\u4f1a\u548c\u4e00\u4e9b\u7b97\u6cd5\u8fdb\u884c\u642d\u914d\u4f7f\u7528\u5427\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Memoization \u5e94\u8be5\u6709\u5f88\u5927\u7684\u4f7f\u7528\u573a\u666f\u7684\uff0c\u4e3e\u4e2a\u4f8b\u5b50\u3002\u6211\u4eec\u73b0\u5728\u8981\u7b97\u4e00\u4e2a\u6590\u6ce2\u90a3\u5951\u6570\u5217\uff0c\u5bf9\u4e8e\u4e00\u4e2a\u5df2\u7ecf\u7b97\u8fc7\u7684\u6570\uff0c\u5c31\u6ca1\u5fc5\u8981\u518d\u8fdb\u884c\u8ba1\u7b97\u4e00\u904d\u4e86\u3002\u6211\u4eec\u53ef\u4ee5\u628a\u8fd9\u4e2a\u6570\u4e4b\u524d\u7b97\u8fc7\u7684\u7ed3\u679c\u4ece\u7f13\u5b58\u4e2d\u53d6\u51fa\u6765\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u6bd4\u5982\u7c7b\u4f3c\u4e0b\u9762\u7684\u6590\u6ce2\u90a3\u5951\u6570\u5217\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>0,1,1,2,3,5,8,13,21,34,55,89,144 ..<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u5b83\u4eec\u5177\u6709\u4ee5\u4e0b\u9012\u5f52\u5173\u7cfb\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>F\uff08n\uff09= F\uff08n-1\uff09+ F\uff08n-2\uff09<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u5728 Java \u4e2d\u6211\u4eec\u53ef\u4ee5\u9760\u9012\u5f52\u51fd\u6570\u6765\u5b9e\u73b0\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>\/\/ Fibonacci without Memoization\npublic int fibonacci(int n){\n\t\n\tif( n == 0 ) return 0;\n\tif( n == 1 ) return 1;\n\t\n\tSystem.out.println(\"Calculating fibonacci number for: \"+n);\n\treturn (fibonacci(n-1) + fibonacci(n-2));\t\n}<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u73b0\u5728\uff0c\u6211\u4eec\u53ef\u4ee5\u8f93\u5165\u4efb\u610f\u6570\u8fdb\u884c\u8ba1\u7b97\u3002\u4f46\u662f\uff0c\u5f53\u6211\u91cd\u590d\u8ba1\u7b97\u4e00\u4e2a\u6570\u65f6\uff0c\u5b83\u5e76\u6ca1\u6709\u8bb0\u5fc6\uff0c\u5e76\u6ca1\u6709\u8bb0\u4f4f\u4e0a\u6b21\u5bf9\u8be5\u6570\u8ba1\u7b97\u5bf9\u7ed3\u679c\u3002\u8fd8\u662f\u4f1a\u4e00\u5c42\u4e00\u5c42\u7684\u9012\u5f52\u8ba1\u7b97\u3002<\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><img decoding=\"async\" src=\"https:\/\/java2blog.com\/wp-content\/uploads\/2018\/08\/FibonacciMemoizationExample.jpg\" alt=\"\" \/><figcaption>\u9012\u5f52\u6811<\/figcaption><\/figure><\/div>\n\n\n\n<p class=\"wp-block-paragraph\">\u89e3\u51b3\u8fd9\u7c7b\u95ee\u9898\u7684\u529e\u6cd5\u5c31\u662f\uff0c\u91c7\u7528\u7f13\u5b58\uff0c\u628a\u4e4b\u524d\u8ba1\u7b97\u8fc7\u7684\u6570\u5b57\u76f4\u63a5\u7f13\u5b58\u8d77\u6765\u3002\u4e0b\u6b21\u518d\u8c03\u7528\u5c31\u5148\u5224\u65ad\u7f13\u5b58\u4e2d\u662f\u5426\u6709\u6ca1\u6709\uff0c\u6ca1\u6709\u7684\u5316\u518d\u8ba1\u7b97\uff0c\u5426\u5219\u76f4\u63a5\u4ece\u7f13\u5b58\u4e2d\u8bfb\u53d6\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>public class FibonacciMemoizationAlgorithm {\n\tprivate Map&lt;Integer, Integer&gt; memoizeTable = new HashMap&lt;&gt;(); \/\/ O(1)\n\t\/\/ Fibonacci with Memoization\n\tpublic int fibonacciMemoize(int n){\n\t\tif( n == 0 ) return 0;\n\t\tif( n == 1 ) return 1;\n\t\tif( this.memoizeTable.containsKey(n) ) {\n\t\t\tSystem.out.println(\"Getting value from computed result for \"+n);\n\t\t\treturn this.memoizeTable.get(n);\n\t\t}\n\t\tint result = fibonacciMemoize(n-1)+ fibonacciMemoize(n-2);\n\t\tSystem.out.println(\"Putting result in cache for \"+n);\n\t\tthis.memoizeTable.put(n, result);\n\t\treturn result;\n\t}\n\t\/\/ Fibonacci without Memoization\n\tpublic int fibonacci(int n){\n\t\tif( n == 0 ) return 0;\n\t\tif( n == 1 ) return 1;\n\t\tSystem.out.println(\"Calculating fibonacci number for: \"+n);\n\t\treturn (fibonacci(n-1) + fibonacci(n-2));\t\n\t}\n\tpublic static void main(String[] args) {\n\t\tFibonacciMemoizationAlgorithm fibonacciAlgorithm = new FibonacciMemoizationAlgorithm();\n\t\tSystem.out.println(\"Fibonacci value for n=5:  \"+fibonacciAlgorithm.fibonacciMemoize(5));\n \n\t}\n}<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u8fd9\u5c31\u662f\u8bb0\u5fc6\u5316\u7684\u539f\u7406\uff0c\u4e0d\u540c\u7684\u573a\u666f\u91c7\u7528\u7684\u7f13\u5b58\u6280\u672f\u4e0d\u540c\uff0c\u4f46\u539f\u7406\u57fa\u672c\u90fd\u7c7b\u4f3c\u3002<\/p>\n<!-- <audio autoplay=\"autoplay\" height=\"100\" width=\"100\" hidden=\"true\"><source src=\"https:\/\/c.coka.la\/orAvPR.mp3\" type=\"audio\/mp3\"\/><\/audio><img decoding=\"async\" src=\"https:\/\/images.weserv.nl\/?url=https:\/\/ws3.sinaimg.cn\/large\/8fa5dcfcgy1g4em3rzar5j20ib089ae0.jpg\" alt=\"\u4e1a\u4f59\u8349\u516c\u4f17\u53f7\"\/> --><p><!-- <img decoding=\"async\" src=\"https:\/\/raw.githubusercontent.com\/xmt1139057136\/xttblog\/master\/8fa5dcfcgy1g4em3rzar5j20ib089ae0.jpg\" alt=\"\u4e1a\u4f59\u8349\u516c\u4f17\u53f7\"\/>--><img decoding=\"async\" src=\"https:\/\/saas.51autoparts.cn\/api\/admin\/sys-file\/oss\/file?fileName=84db51f8561e448f9a4fda2eff0811f9.jpg\" alt=\"\u4e1a\u4f59\u8349\u516c\u4f17\u53f7\"\/><\/p><p>\u6700\u540e\uff0c\u6b22\u8fce\u5173\u6ce8\u6211\u7684\u4e2a\u4eba\u5fae\u4fe1\u516c\u4f17\u53f7\uff1a\u4e1a\u4f59\u8349\uff08yyucao\uff09\uff01<b>\u53ef\u52a0\u4f5c\u8005\u5fae\u4fe1\u53f7\uff1a<font color=\"red\">xttblog2<\/font>\u3002\u5907\u6ce8\uff1a\u201c1\u201d\uff0c\u6dfb\u52a0\u535a\u4e3b\u5fae\u4fe1\u62c9\u4f60\u8fdb\u5fae\u4fe1\u7fa4\u3002\u5907\u6ce8\u9519\u8bef\u4e0d\u4f1a\u540c\u610f\u597d\u53cb\u7533\u8bf7\u3002<\/b>\u518d\u6b21\u611f\u8c22\u60a8\u7684\u5173\u6ce8\uff01\u540e\u7eed\u6709\u7cbe\u5f69\u5185\u5bb9\u4f1a\u7b2c\u4e00\u65f6\u95f4\u53d1\u7ed9\u60a8\uff01\u539f\u521b\u6587\u7ae0\u6295\u7a3f\u8bf7\u53d1\u9001\u81f3532009913@qq.com\u90ae\u7bb1\u3002\u5546\u52a1\u5408\u4f5c\u4e5f\u53ef\u6dfb\u52a0\u4f5c\u8005\u5fae\u4fe1\u8fdb\u884c\u8054\u7cfb\uff01<\/p><p>\u672c\u6587\u539f\u6587\u51fa\u5904\uff1a<a href=\"https:\/\/www.xttblog.com\">\u4e1a\u4f59\u8349<\/a>\uff1a &raquo; <a href=\"https:\/\/www.xttblog.com\/?p=4980\">Java\u4e2d\u7684\u8bb0\u5fc6(Memoization)\u7b97\u6cd5<\/a><\/p><!-- <div class=\"bd-reward-stl\"><button id=\"bdRewardBtn\"><span><\/span><\/button><\/div> -->","protected":false},"excerpt":{"rendered":"<p>Memoization \u88ab\u5f88\u591a\u4eba\u7ffb\u8bd1\u6210\u8bb0\u5fc6\uff0c\u662f\u6839\u636e\u5b57\u9762\u610f\u601d\u6765\u7ffb\u8bd1\u7684\u3002\u4eca\u5929\u6211\u5c31\u6765\u8bf4\u4e00\u8bf4\u8bb0\u5fc6\u5316\u7b97\u6cd5\u3002 \u5b83\u5176\u5b9e\u662f\u4e00\u79cd [&hellip;]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5],"tags":[871,1610,872,172,75],"class_list":["post-4980","post","type-post","status-publish","format-standard","hentry","category-java","tag-idea","tag-rete","tag-872","tag-172","tag-75"],"_links":{"self":[{"href":"https:\/\/www.xttblog.com\/index.php?rest_route=\/wp\/v2\/posts\/4980","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.xttblog.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.xttblog.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.xttblog.com\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.xttblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=4980"}],"version-history":[{"count":1,"href":"https:\/\/www.xttblog.com\/index.php?rest_route=\/wp\/v2\/posts\/4980\/revisions"}],"predecessor-version":[{"id":4981,"href":"https:\/\/www.xttblog.com\/index.php?rest_route=\/wp\/v2\/posts\/4980\/revisions\/4981"}],"wp:attachment":[{"href":"https:\/\/www.xttblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=4980"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.xttblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=4980"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.xttblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=4980"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}