{"id":6415,"date":"2020-03-08T11:54:20","date_gmt":"2020-03-08T18:54:20","guid":{"rendered":"https:\/\/zxi.mytechroad.com\/blog\/?p=6415"},"modified":"2020-03-08T11:54:54","modified_gmt":"2020-03-08T18:54:54","slug":"leetcode-1375-bulb-switcher-iii","status":"publish","type":"post","link":"https:\/\/zxi.mytechroad.com\/blog\/algorithms\/array\/leetcode-1375-bulb-switcher-iii\/","title":{"rendered":"\u82b1\u82b1\u9171 LeetCode 1375. Bulb Switcher III"},"content":{"rendered":"\n

There is a room with n<\/code> bulbs, numbered from 1<\/code> to n<\/code>, arranged in a row from left to right. Initially, all the bulbs are turned off.<\/p>\n\n\n\n

At moment k<\/em> (for k<\/em> from 0<\/code> to n - 1<\/code>), we turn on the light[k]<\/code> bulb. A bulb change color to blue<\/strong> only if it is on and all the previous bulbs (to the left) are turned on too.<\/p>\n\n\n\n

Return the number of moments in which all turned on<\/strong> bulbs are blue.<\/strong><\/p>\n\n\n\n

Example 1:<\/strong><\/p>\n\n\n\n

\"\"\/<\/figure>\n\n\n\n
Input:<\/strong> light = [2,1,3,5,4]\nOutput:<\/strong> 3\nExplanation:<\/strong> All bulbs turned on, are blue at the moment 1, 2 and 4.\n<\/pre>\n\n\n\n
Example 2:<\/strong><\/p>\n\n\n\n
Input:<\/strong> light = [3,2,4,1,5]\nOutput:<\/strong> 2\nExplanation:<\/strong> All bulbs turned on, are blue at the moment 3, and 4 (index-0).\n<\/pre>\n\n\n\n
Example 3:<\/strong><\/p>\n\n\n\n
Input:<\/strong> light = [4,1,2,3]\nOutput:<\/strong> 1\nExplanation:<\/strong> All bulbs turned on, are blue at the moment 3 (index-0).\nBulb 4th changes to blue at the moment 3.\n<\/pre>\n\n\n\n
Example 4:<\/strong><\/p>\n\n\n\n
Input:<\/strong> light = [2,1,4,3,6,5]\nOutput:<\/strong> 3\n<\/pre>\n\n\n\n
Example 5:<\/strong><\/p>\n\n\n\n
Input:<\/strong> light = [1,2,3,4,5,6]\nOutput:<\/strong> 6\n<\/pre>\n\n\n\n
Constraints:<\/strong><\/p>\n\n\n\n
  • n == light.length<\/code><\/li>
  • 1 <= n <= 5 * 10^4<\/code><\/li>
  • light<\/code> is a permutation of  [1, 2, ..., n]<\/code><\/li><\/ul>\n\n\n\n
    Solution<\/strong><\/h2>\n\n\n\n
    Track the right most light l_k, all turned-on lights are blue if and only if the right most one is k, and there are exact k lights on right now.<\/p>\n\n\n\n
    Time complexity: O(n)
    Space complexity: O(1)<\/p>\n\n\n\n
    \n
    C++<\/h2>\n
    \n\n
    \n\/\/ Author: Huahua\nclass Solution {\npublic:\n  int numTimesAllBlue(vector& light) {    \n    int ans = 0;\n    int right = 0;\n    for (int i = 0; i < light.size(); ++i) {\n      right = max(right, light[i]);\n      ans += right == i + 1;\n    }\n    return ans;\n  }\n};\n<\/pre>\n<\/div><\/div>\n","protected":false},"excerpt":{"rendered":"
    There is a room with n bulbs, numbered from 1 to n, arranged in a row from left to right. Initially, all the bulbs are turned off. At moment k (for k from 0 to n -…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[184],"tags":[20,376],"class_list":["post-6415","post","type-post","status-publish","format-standard","hentry","category-array","tag-array","tag-on","entry","simple"],"_links":{"self":[{"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/posts\/6415","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=6415"}],"version-history":[{"count":3,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/posts\/6415\/revisions"}],"predecessor-version":[{"id":6418,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/posts\/6415\/revisions\/6418"}],"wp:attachment":[{"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/media?parent=6415"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/categories?post=6415"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/tags?post=6415"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}