Problem
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 lexicographicaly 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).
Note:
1 <= words.length <= 100
1 <= words[i].length <= 20
order.length == 26
- All characters in
words[i]
andorder
are english lowercase letters.
Solution: Hashtable
Time complexity: O(sum(len(words[i])))
Space complexity: O(26)
C++
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// Author: Huahua, 8 ms class Solution { public: bool isAlienSorted(vector<string>& words, string order) { vector<char> m(26); for (int i = 0; i < 26; ++i) m[order[i] - 'a'] = 'a' + i; for (int i = 0; i < words.size(); ++i) { for (int j = 0; j < words[i].length(); ++j) words[i][j] = m[words[i][j] - 'a']; if (i > 0 && words[i] < words[i - 1]) return false; } return true; } }; |
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