[Swift Weekly Contest 114]LeetCode953. 验证外星语词典 | 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 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. 1 <= words.length <= 100
2. 1 <= words[i].length <= 20
3. order.length == 26
4. All characters in words[i] and order are english lowercase letters.

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。

示例 1：

输入：words = ["hello",order = "hlabcdefgijkmnopqrstuvwxyz"
输出：true
解释：在该语言的字母表中，‘h‘ 位于 ‘l‘ 之前，所以单词序列是按字典序排列的。

示例 2：

输入：words = ["word",order = "worldabcefghijkmnpqstuvxyz"
输出：false
解释：在该语言的字母表中，‘d‘ 位于 ‘l‘ 之后，那么 words[0] > words[1]，因此单词序列不是按字典序排列的。

示例 3：

输入：words = ["apple",order = "abcdefghijklmnopqrstuvwxyz"
输出：false
解释：当前三个字符 "app" 匹配时，第二个字符串相对短一些，然后根据词典编纂规则 "apple" > "app"，因为 ‘l‘ > ‘∅‘，其中 ‘∅‘ 是空白字符，定义为比任何其他字符都小（更多信息）。

提示：

1. 1 <= words.length <= 100
2. 1 <= words[i].length <= 20
3. order.length == 26
4. 在 words[i] 和 order 中的所有字符都是英文小写字母。

72ms

 1 class Solution {
 2     func isAlienSorted(_ words: [String],_ order: String) -> Bool {
 3         var words = words
 4         var a:[Int] = [Int](repeating:0,count:256)
 5         var i:Int = 0
 6         var j:Int = 0
 7         for i in 0..<order.count
 8         {
 9             a[order.toInt(i)] = i
10         }
11         for i in 0..<words.count
12         {
13             for j in 0..<words[i].count
14             {
15                 //a:97
16                 words[i][j] = (a[words[i][j].ascii] + 97).ASCII
17             }
18         }
19          for i in 0..<(words.count - 1)
20         {
21             if words[i] > words[i+1]
22             {
23                 return false
24             }
25         }
26         return true
27     }
28 }
29 
30 extension String {    
31     //获取指定索引位置的字符，返回为字符串形式
32     func charat(_ num:Int) -> String
33     {
34         return String(self[index(self.startIndex,offsetBy: num)]) 
35     }
36     
37     //获取指定索引位置字符的ASCII整数值
38     func toInt(_ num:Int) -> Int
39     {
40         let s = charat(num).unicodeScalars
41         return Int(s[s.startIndex].value) 
42     }
43     
44     //subscript函数可以检索数组中的值
45     //直接按照索引方式截取指定索引的字符
46     subscript (_ i: Int) -> Character {
47         //读取字符
48         get {return self[index(startIndex,offsetBy: i)]}
49         
50         //修改字符
51         set
52         {
53             var str:String = self
54             var index = str.index(startIndex,offsetBy: i)
55             str.remove(at: index)
56             str.insert(newValue,at: index)
57             self = str
58         }
59     }
60 }
61 
62 //Character扩展方法  
63 extension Character  
64 {  
65   //属性：ASCII整数值(定义小写为整数值)
66    var ascii: Int {
67         get {
68             let s = String(self).unicodeScalars
69             return Int(s[s.startIndex].value)
70         }
71     }
72 }
73 
74 //Int扩展方法  
75 extension Int
76 {
77     //属性：ASCII值(定义大写为字符值)
78     var ASCII:Character 
79     {
80         get {return Character(UnicodeScalar(self)!)}
81     }
82 }