{"id":484,"date":"2012-07-30T21:39:56","date_gmt":"2012-07-31T01:39:56","guid":{"rendered":"http:\/\/www.joshho.com\/blog\/?p=484"},"modified":"2012-09-07T16:15:24","modified_gmt":"2012-09-07T20:15:24","slug":"project-euler-problem-23","status":"publish","type":"post","link":"https:\/\/www.joshho.com\/blog\/2012\/07\/30\/project-euler-problem-23\/","title":{"rendered":"Project Euler &#8211; Problem 23"},"content":{"rendered":"<p>Problem 23: Find the sum of all the positive integers which cannot be written as the sum of two abundant numbers.<br \/>\n<!--more--><br \/>\n<code><\/p>\n<pre lang=\"java\">\r\nclass runner\r\n{\r\n\tprivate static boolean isAbundant(int n){\r\n\t\tint sum = 1;\r\n\t\tfor(int i = 2; i<=Math.sqrt(n); i++){\r\n\t\t\tif(n % i == 0){\r\n\t\t\t\tsum += i;\r\n\t\t\t\t\r\n\t\t\t\tint div = n\/i;\r\n\t\t\t\tif(div != i){\r\n\t\t\t\t\tsum += div;\r\n\t\t\t\t}\r\n\t\t\t}\r\n\t\t}\r\n\t\tif(sum > n) return true;\r\n\t\treturn false;\r\n\t}\r\n\r\n\r\n\tpublic static void main (String[] args) throws java.lang.Exception\r\n\t{\r\n\t\tfinal int max_limit = 28123;\r\n\t\tlong time = System.currentTimeMillis();\r\n\t\tboolean[] arr = new boolean[max_limit+1];\r\n\t\t\r\n\t\tfor(int i = 1; i <= max_limit; i++){\r\n\t\t\tif(isAbundant(i)){\r\n\t\t\t\tarr[i] = true;\r\n\t\t\t}\r\n\t\t}\r\n\r\n\t\tint sum = 0;\r\n\t\tfor(int i=1;i <= max_limit; i++){\r\n\t\t\tboolean match = true;\r\n\t\t\tfor(int z=12; z<arr.length; z++){\r\n\t\t\t\tif(!arr[z]) continue;\r\n\t\t\t\tif(i <= z) {\r\n\t\t\t\t\tbreak;\r\n\t\t\t\t}\r\n\t\t\t\tif(arr[i - z]){\r\n\t\t\t\t\tmatch = false;\r\n\t\t\t\t\tbreak;\r\n\t\t\t\t}\r\n\t\t\t}\r\n\t\t\tif(match) sum += i;\r\n\t\t\t\r\n\t\t}\r\n\t\tSystem.out.println(sum);\r\n\t\t\r\n\t\tSystem.out.println(\"time: \"+(System.currentTimeMillis() - time));\r\n\t}\r\n}\r\n<\/pre>\n<p><\/code><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Problem 23: Find the sum of all the positive integers which cannot be written as the sum of two abundant numbers.<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[56],"tags":[],"_links":{"self":[{"href":"https:\/\/www.joshho.com\/blog\/wp-json\/wp\/v2\/posts\/484"}],"collection":[{"href":"https:\/\/www.joshho.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.joshho.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.joshho.com\/blog\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.joshho.com\/blog\/wp-json\/wp\/v2\/comments?post=484"}],"version-history":[{"count":0,"href":"https:\/\/www.joshho.com\/blog\/wp-json\/wp\/v2\/posts\/484\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.joshho.com\/blog\/wp-json\/wp\/v2\/media?parent=484"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.joshho.com\/blog\/wp-json\/wp\/v2\/categories?post=484"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.joshho.com\/blog\/wp-json\/wp\/v2\/tags?post=484"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}