{"id":23,"date":"2017-03-15T19:22:06","date_gmt":"2017-03-16T02:22:06","guid":{"rendered":"http:\/\/zxi.mytechroad.com\/blog\/?p=23"},"modified":"2018-04-19T08:42:46","modified_gmt":"2018-04-19T15:42:46","slug":"leetcode-longest-consecutive-sequence","status":"publish","type":"post","link":"https:\/\/zxi.mytechroad.com\/blog\/zoj\/leetcode-longest-consecutive-sequence\/","title":{"rendered":"\u82b1\u82b1\u9171 LeetCode 128. Longest Consecutive Sequence"},"content":{"rendered":"<p>Given an unsorted array of integers, find the length of the longest consecutive elements sequence.<\/p>\n<p>For example,<br \/>\nGiven <code>[100, 4, 200, 1, 3, 2]<\/code>,<br \/>\nThe longest consecutive elements sequence is <code>[1, 2, 3, 4]<\/code>. Return its length: <code>4<\/code>.<\/p>\n<p>Your algorithm should run in O(<i>n<\/i>) complexity.<\/p>\n<pre class=\"lang:c++ decode:true\">class Solution {\r\npublic:\r\n    int longestConsecutive(vector&lt;int&gt; &amp;num) {\r\n        unordered_map&lt;int,int&gt; m;\r\n        int ans = 0;\r\n        for(auto n : num) {\r\n            if(m.count(n)) continue;\r\n            if(m.count(n-1) &amp;&amp; m.count(n+1)){\r\n                int l = m[n-1], r = m[n+1];\r\n                m[n] = m[n-l] = m[n+r] = r+l+1;\r\n            } else if(m.count(n-1)) {\r\n                int l = m[n-1];\r\n                m[n] = m[n-l] = l+1; \r\n            } else if(m.count(n+1)) {\r\n                int r = m[n+1];\r\n                m[n] = m[n+r] = r+1;\r\n            } else {\r\n                m[n] = 1;\r\n            }\r\n            ans = max(ans, m[n]);\r\n        }\r\n        return ans;\r\n    }\r\n};<\/pre>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Given an unsorted array of integers, find the length of the longest consecutive elements sequence. For example, Given [100, 4, 200, 1, 3, 2], The&#8230;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[9],"tags":[18,19],"class_list":["post-23","post","type-post","status-publish","format-standard","hentry","category-zoj","tag-dp","tag-hashmap","entry","simple"],"_links":{"self":[{"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/posts\/23","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/comments?post=23"}],"version-history":[{"count":3,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/posts\/23\/revisions"}],"predecessor-version":[{"id":2730,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/posts\/23\/revisions\/2730"}],"wp:attachment":[{"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/media?parent=23"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/categories?post=23"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/tags?post=23"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}