[Swift]LeetCode389. 找不同 | Find the Difference

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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.

---

给定两个字符串 s 和 t，它们只包含小写字母。

字符串 t 由字符串 s 随机重排，然后在随机位置添加一个字母。

请找出在 t 中被添加的字母。

 

示例:

输入：
s = "abcd"
t = "abcde"

输出：
e

解释：
'e' 是那个被添加的字母。

---

24ms

class Solution {
    func findTheDifference(_ s: String, _ t: String) -> Character {
        var num_s:UInt32 = getUInt32Value(s)
        var num_t:UInt32 = getUInt32Value(t)
        //Int转Character：Character(UnicodeScalar(number)) 
        return Character(UnicodeScalar(num_t - num_s)!) 
    }
    //获取字符串的所有字符的ASCII整形之和
    func getUInt32Value(_ str:String) -> UInt32
    {
        var num:UInt32 = UInt32()
        //Character转Int：for asc in String(char).unicodeScalars
        for asc in str.unicodeScalars
        {  
            num += asc.value
        } 
        return num
    }
}
    //Character扩展代码  
    extension Character  
    {  
        func toInt() -> Int  
        {  
            var num:Int = Int()
            for scalar in String(self).unicodeScalars  
            {  
                num = Int(scalar.value)  
            }  
            return num  
        }  
    } 

---

76ms

class Solution {
    func findTheDifference(_ s: String, _ t: String) -> Character {
        var num_s:UInt32 = getUInt32Value(s)
        var num_t:UInt32 = getUInt32Value(t)
        //Int转Character：Character(UnicodeScalar(number)) 
        return Character(UnicodeScalar(num_t - num_s)!) 
    }
    //获取字符串的所有字符的ASCII整型之和
    func getUInt32Value(_ str:String) -> UInt32
    {
        var num:UInt32 = UInt32()
        //Character转Int：for asc in String(char).unicodeScalars
        for asc in str.unicodeScalars
        {  
            num += asc.value
        } 
        return num
    }
}
    //Character扩展代码  
    extension Character  
    {  
        func toInt() -> Int  
        {  
            var num:Int = Int()
            for scalar in String(self).unicodeScalars  
            {  
                num = Int(scalar.value)  
            }  
            return num  
        }  
    } 

---

104ms

class Solution {
    func findTheDifference(_ s: String, _ t: String) -> Character {
        
        
        var s = s.sorted()
        var t = t.sorted()
        for i in 0..<s.count {
            
            let startIndex = s.index(s.startIndex, offsetBy: i)
            let endIndex = s.index(s.startIndex, offsetBy: i + 1)
            let a = String(s[startIndex..<endIndex])
            
            
            let startIndexT = t.index(t.startIndex, offsetBy: i)
            let endIndexT = t.index(t.startIndex, offsetBy: i + 1)
            let b = String(t[startIndexT..<endIndexT])
            
            if a != b {
                return Character(b)
            }
            
        }
        
        return t.last ?? " "
    }
}