{"id":7592,"date":"2020-10-31T23:36:09","date_gmt":"2020-11-01T06:36:09","guid":{"rendered":"https:\/\/zxi.mytechroad.com\/blog\/?p=7592"},"modified":"2020-11-01T00:19:19","modified_gmt":"2020-11-01T07:19:19","slug":"leetcode-1640-check-array-formation-through-concatenation","status":"publish","type":"post","link":"https:\/\/zxi.mytechroad.com\/blog\/hashtable\/leetcode-1640-check-array-formation-through-concatenation\/","title":{"rendered":"\u82b1\u82b1\u9171 LeetCode 1640. Check Array Formation Through Concatenation"},"content":{"rendered":"\n

You are given an array of distinct<\/strong> integers arr<\/code> and an array of integer arrays pieces<\/code>, where the integers in pieces<\/code> are distinct<\/strong>. Your goal is to form arr<\/code> by concatenating the arrays in pieces<\/code> in any order<\/strong>. However, you are not<\/strong> allowed to reorder the integers in each array pieces[i]<\/code>.<\/p>\n\n\n\n

Return true<\/code> if it is possible <\/em>to form the array <\/em>arr<\/code> from <\/em>pieces<\/code>. Otherwise, return false<\/code>.<\/p>\n\n\n\n

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

Input:<\/strong> arr = [85], pieces = [[85]]\nOutput:<\/strong> true\n<\/pre>\n\n\n\n
Example 2:<\/strong><\/p>\n\n\n\n
Input:<\/strong> arr = [15,88], pieces = [[88],[15]]\nOutput:<\/strong> true\nExplanation:<\/strong> Concatenate [15]<\/code> then [88]<\/code>\n<\/pre>\n\n\n\n
Example 3:<\/strong><\/p>\n\n\n\n
Input:<\/strong> arr = [49,18,16], pieces = [[16,18,49]]\nOutput:<\/strong> false\nExplanation:<\/strong> Even though the numbers match, we cannot reorder pieces[0].\n<\/pre>\n\n\n\n
Example 4:<\/strong><\/p>\n\n\n\n
Input:<\/strong> arr = [91,4,64,78], pieces = [[78],[4,64],[91]]\nOutput:<\/strong> true\nExplanation:<\/strong> Concatenate [91]<\/code> then [4,64]<\/code> then [78]<\/code><\/pre>\n\n\n\n
Example 5:<\/strong><\/p>\n\n\n\n
Input:<\/strong> arr = [1,3,5,7], pieces = [[2,4,6,8]]\nOutput:<\/strong> false\n<\/pre>\n\n\n\n
Constraints:<\/strong><\/p>\n\n\n\n
  • 1 <= pieces.length <= arr.length <= 100<\/code><\/li>
  • sum(pieces[i].length) == arr.length<\/code><\/li>
  • 1 <= pieces[i].length <= arr.length<\/code><\/li>
  • 1 <= arr[i], pieces[i][j] <= 100<\/code><\/li>
  • The integers in arr<\/code> are distinct<\/strong>.<\/li>
  • The integers in pieces<\/code> are distinct<\/strong> (i.e., If we flatten pieces in a 1D array, all the integers in this array are distinct).<\/li><\/ul>\n\n\n\n
    Solution: Hashtable<\/strong><\/h2>\n\n\n\n
    Store the index of the first number of each piece, for each number a in arr, concat the entire piece array whose first element equals to a.<\/p>\n\n\n\n
    Time complexity: O(n)
    Space complexity: O(n)<\/p>\n\n\n\n
    \n
    C++<\/h2>\n
    \n\n
    \nclass Solution {\npublic:\n  bool canFormArray(vector& arr, vector>& pieces) {\n    unordered_map m;\n    for (int i = 0; i < pieces.size(); ++i)\n      m[pieces[i][0]] = i;\n    \n    vector ans;\n    for (int a : arr) {\n      if (!m.count(a)) continue;\n      ans.insert(end(ans), begin(pieces[m[a]]), end(pieces[m[a]]));\n    }\n    \n    return ans == arr;\n  }\n};\n<\/pre>\n<\/div><\/div>\n","protected":false},"excerpt":{"rendered":"
    You are given an array of distinct integers arr and an array of integer arrays pieces, where the integers in pieces are distinct. Your goal is to form arr by concatenating the arrays in pieces in any…<\/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":[20,222,82],"class_list":["post-7592","post","type-post","status-publish","format-standard","hentry","category-hashtable","tag-array","tag-easy","tag-hashtable","entry","simple"],"_links":{"self":[{"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/posts\/7592","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=7592"}],"version-history":[{"count":2,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/posts\/7592\/revisions"}],"predecessor-version":[{"id":7594,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/posts\/7592\/revisions\/7594"}],"wp:attachment":[{"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/media?parent=7592"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/categories?post=7592"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/tags?post=7592"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}