[Swift]LeetCode389. 找不一樣 | Find the Difference

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➤微信公衆號：山青詠芝（shanqingyongzhi）
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➤GitHub地址：https://github.com/strengthen/LeetCode
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Given two strings s and t which consist of only lowercase letters.

String t is generated by random shuffling string s and then add one more letter at a random position.

Find the letter that was added in t.

Example:

Input:
s = "abcd"
t = "abcde"

Output:
e

Explanation:
'e' is the letter that was added.

---

給定兩個字符串 s 和 t，它們只包含小寫字母。

字符串 t 由字符串 s 隨機重排，而後在隨機位置添加一個字母。

請找出在 t 中被添加的字母。

 

示例:

輸入：
s = "abcd"
t = "abcde"

輸出：
e

解釋：
'e' 是那個被添加的字母。

---

24ms

 1 class Solution {
 2     func findTheDifference(_ s: String, _ t: String) -> Character {
 3         var num_s:UInt32 = getUInt32Value(s)
 4         var num_t:UInt32 = getUInt32Value(t)
 5         //Int轉Character：Character(UnicodeScalar(number)) 
 6         return Character(UnicodeScalar(num_t - num_s)!) 
 7     }
 8     //獲取字符串的全部字符的ASCII整形之和
 9     func getUInt32Value(_ str:String) -> UInt32
10     {
11         var num:UInt32 = UInt32()
12         //Character轉Int：for asc in String(char).unicodeScalars
13         for asc in str.unicodeScalars
14         {  
15             num += asc.value
16         } 
17         return num
18     }
19 }
20     //Character擴展代碼  
21     extension Character  
22     {  
23         func toInt() -> Int  
24         {  
25             var num:Int = Int()
26             for scalar in String(self).unicodeScalars  
27             {  
28                 num = Int(scalar.value)  
29             }  
30             return num  
31         }  
32     } 

---

76ms

 1 class Solution {
 2     func findTheDifference(_ s: String, _ t: String) -> Character {
 3         var num_s:UInt32 = getUInt32Value(s)
 4         var num_t:UInt32 = getUInt32Value(t)
 5         //Int轉Character：Character(UnicodeScalar(number)) 
 6         return Character(UnicodeScalar(num_t - num_s)!) 
 7     }
 8     //獲取字符串的全部字符的ASCII整型之和
 9     func getUInt32Value(_ str:String) -> UInt32
10     {
11         var num:UInt32 = UInt32()
12         //Character轉Int：for asc in String(char).unicodeScalars
13         for asc in str.unicodeScalars
14         {  
15             num += asc.value
16         } 
17         return num
18     }
19 }
20     //Character擴展代碼  
21     extension Character  
22     {  
23         func toInt() -> Int  
24         {  
25             var num:Int = Int()
26             for scalar in String(self).unicodeScalars  
27             {  
28                 num = Int(scalar.value)  
29             }  
30             return num  
31         }  
32     } 

---

104ms

 1 class Solution {
 2     func findTheDifference(_ s: String, _ t: String) -> Character {
 3         
 4         
 5         var s = s.sorted()
 6         var t = t.sorted()
 7         for i in 0..<s.count {
 8             
 9             let startIndex = s.index(s.startIndex, offsetBy: i)
10             let endIndex = s.index(s.startIndex, offsetBy: i + 1)
11             let a = String(s[startIndex..<endIndex])
12             
13             
14             let startIndexT = t.index(t.startIndex, offsetBy: i)
15             let endIndexT = t.index(t.startIndex, offsetBy: i + 1)
16             let b = String(t[startIndexT..<endIndexT])
17             
18             if a != b {
19                 return Character(b)
20             }
21             
22         }
23         
24         return t.last ?? " "
25     }
26 }