Description
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.
某种外星语也使用英文小写字母，但可能顺序 order 不同。字母表的顺序（order）是一些小写字母的排列。
给定一组用外星语书写的单词 words，以及其字母表的顺序 order，只有当给定的单词在这种外星语中按字典序排列时，返回 true；否则，返回 false。
题目链接：https://leetcode.com/problems/verifying-an-alien-dictionary/
Difficulty: easy
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] and order are english lowercase letters.
分析
- 定义一个判断符合‘order’顺序的函数judge，遍历w1，w2，若w1在大于w2，返回False，若w1在小于w2，返回True，反之继续；
- 将‘order’存入字典，保存其序号，用于judge中判断；
- 遍历‘words’，用judge判断，若存在逆序，返回False；
- 返回True。
参考代码
class Solution:
def isAlienSorted(self, words, order):
def judge(w1,w2,o):
i=0
while(i<len(w1) and i < len(w2)):
if(o[w1[i]] < o[w2[i]]):
return True
elif(o[w1[i]]>o[w2[i]]):
return False
else:
i+=1
if(i<len(w1)):
return False
else:
return True
o={}
for i in range(len(order)):
o[order[i]]=i
for i in range(len(words)-1):
if(not judge(words[i],words[i+1],o)):
return False
return True