Today I have done leetcode's February LeetCoding Challenge with cpp.

February LeetCoding Challenge 2

Description

Verifying an Alien Dictionary

In an alien language, surprisingly, they also use English lowercase letters, but possibly in a different order. The order of the alphabet is some permutation of lowercase letters.

Given a sequence of words written in the alien language, and the order of the alphabet, return true if and only if the given words are sorted lexicographically in this alien language.

Example 1:

Input: words = ["hello","leetcode"], order = "hlabcdefgijkmnopqrstuvwxyz"
Output: true
Explanation: As 'h' comes before 'l' in this language, then the sequence is sorted.

Example 2:

Input: words = ["word","world","row"], order = "worldabcefghijkmnpqstuvxyz"
Output: false
Explanation: As 'd' comes after 'l' in this language, then words[0] > words[1], hence the sequence is unsorted.

Example 3:

Input: words = ["apple","app"], order = "abcdefghijklmnopqrstuvwxyz"
Output: false
Explanation: The first three characters "app" match, and the second string is shorter (in size.) According to lexicographical rules "apple" > "app", because 'l' > '∅', where '∅' is defined as the blank character which is less than any other character (More info).

Constraints:

• 1 <= words.length <= 100
• 1 <= words[i].length <= 20
• order.length == 26
• All characters in words[i] and order are English lowercase letters.

Solution

class Solution {
public:
  bool isAlienSorted(vector<string>& words, string order) {
    int orderIndex[128] = {};
    int pos = 0;
    for(auto c : order) orderIndex[c] = pos++;
    return is_sorted(words.begin(), words.end(), [&](const string &a, const string &b) {
      for(int i = 0; i < min(a.length(), b.length()); ++i) {
        if(a[i] != b[i]) return orderIndex[a[i]] < orderIndex[b[i]];
      }
      return a.length() < b.length();
    });
  }
};

// Accepted
// 120/120 cases passed (0 ms)
// Your runtime beats 100 % of cpp submissions
// Your memory usage beats 99.14 % of cpp submissions (9.2 MB)