{"id":6932,"date":"2020-06-14T19:40:03","date_gmt":"2020-06-15T02:40:03","guid":{"rendered":"https:\/\/zxi.mytechroad.com\/blog\/?p=6932"},"modified":"2020-06-14T19:42:25","modified_gmt":"2020-06-15T02:42:25","slug":"leetcode-1481-least-number-of-unique-integers-after-k-removals","status":"publish","type":"post","link":"https:\/\/zxi.mytechroad.com\/blog\/hashtable\/leetcode-1481-least-number-of-unique-integers-after-k-removals\/","title":{"rendered":"\u82b1\u82b1\u9171 LeetCode 1481. Least Number of Unique Integers after K Removals"},"content":{"rendered":"\n

Given an array of integers arr<\/code> and an integer k<\/code>. Find the least number of unique integers<\/em> after removing exactly<\/strong> k<\/code> elements.<\/strong><\/p>\n\n\n\n

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

Input: <\/strong>arr = [5,5,4], k = 1\nOutput: <\/strong>1\nExplanation<\/strong>: Remove the single 4, only 5 is left.\n<\/pre>\n\n\n\n
Example 2:<\/strong><\/p>\n\n\n\n
Input: <\/strong>arr = [4,3,1,1,3,3,2], k = 3\nOutput: <\/strong>2\nExplanation<\/strong>: Remove 4, 2 and either one of the two 1s or three 3s. 1 and 3 will be left.<\/pre>\n\n\n\n
Constraints:<\/strong><\/p>\n\n\n\n
  • 1 <= arr.length <= 10^5<\/code><\/li>
  • 1 <= arr[i] <= 10^9<\/code><\/li>
  • 0 <= k <= arr.length<\/code><\/li><\/ul>\n\n\n\n
    Solution: Greedy<\/strong><\/h2>\n\n\n\n
    Count the frequency of each unique number. Sort by frequency, remove items with lowest frequency first.<\/p>\n\n\n\n
    Time complexity: O(nlogn)
    Space complexity: O(n)<\/p>\n\n\n\n
    \n
    C++<\/h2>\n
    \n\n
    \n\/\/ Author: Huahua\nclass Solution {\npublic:\n  int findLeastNumOfUniqueInts(vector& arr, int k) {    \n    unordered_map c;\n    for (int x : arr) ++c[x];\n    vector m; \/\/ freq\n    for (const auto [x, f] : c)\n      m.push_back(f);\n    sort(begin(m), end(m));\n    int ans = m.size();    \n    int i = 0;\n    while (k--) {\n      if (--m[i] == 0) {\n        ++i;\n        --ans;\n      }\n    }\n    return ans;\n  }\n};\n<\/pre>\n<\/div><\/div>\n","protected":false},"excerpt":{"rendered":"
    Given an array of integers arr and an integer k. Find the least number of unique integers after removing exactly k elements. Example 1: Input: arr = [5,5,4], k = 1 Output: 1 Explanation:…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[70],"tags":[24,88,82,177,23],"class_list":["post-6932","post","type-post","status-publish","format-standard","hentry","category-hashtable","tag-frequency","tag-greedy","tag-hashtable","tag-medium","tag-sort","entry","simple"],"_links":{"self":[{"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/posts\/6932","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=6932"}],"version-history":[{"count":2,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/posts\/6932\/revisions"}],"predecessor-version":[{"id":6934,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/posts\/6932\/revisions\/6934"}],"wp:attachment":[{"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/media?parent=6932"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/categories?post=6932"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/tags?post=6932"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}