[Swift]LeetCode125. 驗證迴文串 | Valid Palindrome

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➤微信公衆號：山青詠芝（shanqingyongzhi）
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Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.

Note: For the purpose of this problem, we define empty string as valid palindrome.

Example 1:

Input: "A man, a plan, a canal: Panama"
Output: true

Example 2:

Input: "race a car"
Output: false

---

給定一個字符串，驗證它是不是迴文串，只考慮字母和數字字符，能夠忽略字母的大小寫。

說明：本題中，咱們將空字符串定義爲有效的迴文串。

示例 1:

輸入: "A man, a plan, a canal: Panama"
輸出: true

示例 2:

輸入: "race a car"
輸出: false

---

28ms

 1 class Solution {
 2     func isPalindrome(_ s: String) -> Bool {
 3         
 4         let lowerS = s.lowercased()
 5         var ints = [UInt32]()
 6         for scalars in lowerS.unicodeScalars {
 7             ints.append(scalars.value)
 8         }
 9         var i = 0
10         var j = ints.count - 1
11         
12         while i < j {
13             if !isCharOrNumber(ints[i]) {
14                 i += 1
15             }else if !isCharOrNumber(ints[j]) {
16                 j -= 1
17             }else if ints[i] != ints[j] {
18                 return false
19             }else {
20                 i += 1
21                 j -= 1
22             }
23         }
24         return true
25 
26     }
27     
28     func isCharOrNumber(_ character: UInt32) -> Bool {
29         if character >= 97 && character <= 122 {
30             return true
31         }
32         
33         if character >= 48 && character <= 57 {
34             return true
35         }
36         return false
37     }
38 }

---

32ms

 1 class Solution {
 2     func isPalindrome(_ s: String) -> Bool {
 3         if s.count == 0 {
 4            return true
 5         }
 6         
 7         var chas = s.cString(using:.ascii)!
 8         
 9         var left = 0
10         var right = s.count - 1
11         
12         var loop = true
13         
14         while loop {
15             if left > right {
16                 loop = false
17                 continue
18             } 
19             
20             let leftChar = chas[left]
21             
22             if !checkIsNormalChar(leftChar) {
23                 left = left + 1
24                 continue
25             }
26             
27             let rightChar = chas[right] 
28             
29             if !checkIsNormalChar(rightChar) {
30                 right = right - 1
31                 continue
32             }
33             
34             if isEqual(leftChar,rightChar) {
35                 left = left + 1
36                 right = right - 1
37             } else {
38                 return false
39             }
40             
41         }
42         return true
43     }
44     
45     func isEqual(_ c:CChar, _ other:CChar) -> Bool {
46         if c == other {
47             return true
48         }
49         var newC = c
50         if c >= 97 {
51             newC = c - 32;
52         }
53         
54         var newOther = other
55         
56         if other >= 97 {
57             newOther = other - 32
58         }
59         
60         return newC == newOther
61     }
62     
63     func checkIsNormalChar(_ c: CChar) -> Bool {
64         if c < 48 {
65             return false
66         }
67         
68         if c > 122 {
69             return false
70         }
71         
72         if c > 57 && c < 65 {
73             return false
74         }
75         
76         if c > 90 && c < 97 {
77             return false
78         }
79         
80         return true
81     }
82 }