{"id":660,"date":"2012-08-18T00:42:22","date_gmt":"2012-08-18T04:42:22","guid":{"rendered":"http:\/\/www.joshho.com\/blog\/?p=660"},"modified":"2012-09-07T16:01:19","modified_gmt":"2012-09-07T20:01:19","slug":"project-euler-problem-63","status":"publish","type":"post","link":"https:\/\/www.joshho.com\/blog\/2012\/08\/18\/project-euler-problem-63\/","title":{"rendered":"Project Euler &#8211; Problem 63"},"content":{"rendered":"<p>Problem 63:<br \/>\nThe 5-digit number, 16807=7^5, is also a fifth power. Similarly, the 9-digit number, 134217728=8^9, is a ninth power.<\/p>\n<p>How many n-digit positive integers exist which are also an nth power?<br \/>\n<!--more--><br \/>\n<code><\/p>\n<pre lang='java'>\r\npackage runner;\r\n\r\nimport java.math.BigInteger;\r\nimport java.util.HashSet;\r\n\r\nclass runner\r\n{\r\n\r\n\tpublic static void main (String[] args) throws java.lang.Exception\r\n\t{\r\n\t\tlong time = System.currentTimeMillis();\r\n\r\n\t\tHashSet<String> store = new HashSet<String>(); \r\n\t\tint power=1;\r\n\r\n\t\tboolean found = true;\r\n\t\twhile(found){\r\n\t\t\tfound = false;\r\n\t\t\tBigInteger base = BigInteger.ONE;\r\n\t\t\tdo{\r\n\t\t\t\tBigInteger r = base.pow(power);\r\n\t\t\t\tif(r.toString().length() > power) break;\r\n\t\t\t\tif(r.toString().length() == power){\r\n\t\t\t\t\tstore.add(r.toString());\r\n\t\t\t\t\tfound = true;\r\n\t\t\t\t}\r\n\t\t\t\tbase = base.add(BigInteger.ONE);\r\n\t\t\t}while(true);\r\n\t\t\tpower++;\r\n\t\t}\r\n\t\tSystem.out.println(store.size());\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 63:<br \/>\nThe 5-digit number, 16807=7^5, is also a fifth power. Similarly, the 9-digit number, 134217728=8^9, is a ninth power.<\/p>\n<p>How many n-digit positive integers exist which are also an nth power?<\/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\/660"}],"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=660"}],"version-history":[{"count":0,"href":"https:\/\/www.joshho.com\/blog\/wp-json\/wp\/v2\/posts\/660\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.joshho.com\/blog\/wp-json\/wp\/v2\/media?parent=660"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.joshho.com\/blog\/wp-json\/wp\/v2\/categories?post=660"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.joshho.com\/blog\/wp-json\/wp\/v2\/tags?post=660"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}