[Swift]LeetCode1002. 查找常用字符 | Find Common Characters - Swift 教程-OStack程序员社区-中国程序员成长平台

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Given an array A of strings made only from lowercase letters, return a list of all characters that show up in all strings within the list (including duplicates). For example, if a character occurs 3 times in all strings but not 4 times, you need to include that character three times in the final answer.

You may return the answer in any order.

Example 1:

Input: ["bella","label","roller"]
Output: ["e","l","l"]

Example 2:

Input: ["cool","lock","cook"]
Output: ["c","o"]

Note:

1 <= A.length <= 100
1 <= A[i].length <= 100
A[i][j] is a lowercase letter

给定仅有小写字母组成的字符串数组 A，返回列表中的每个字符串中都显示的全部字符（包括重复字符）组成的列表。例如，如果一个字符在每个字符串中出现 3 次，但不是 4 次，则需要在最终答案中包含该字符 3 次。

你可以按任意顺序返回答案。

示例 1：

输入：["bella","label","roller"]
输出：["e","l","l"]

示例 2：

输入：["cool","lock","cook"]
输出：["c","o"]

提示：

1 <= A.length <= 100
1 <= A[i].length <= 100
A[i][j] 是小写字母

52ms

 1 class Solution {
 2     func commonChars(_ A: [String]) -> [String] {
 3         if A.count < 1 {
 4         return []
 5     }
 6     
 7     var commonCount: [Int] = Array.init(repeating: 0, count: 26)
 8     var ans:[String] = []
 9     for string in A {
10         var thisFrequency:[Int] = Array.init(repeating: 0, count: 26)
11         var leftIndex  = string.startIndex
12         
13         while leftIndex < string.endIndex {
14             let leftChar  = string[leftIndex]
15             if let value = leftChar.unicodeScalars.first?.value {
16                 let index = Int(value - 97)
17                 thisFrequency[index] += 1
18             }
19             // move towards middle
20             leftIndex  = string.index(after: leftIndex)
21         }
22         if string == A.first {
23             for index in 0...25 {
24                 commonCount[index] = thisFrequency[index]
25             }
26         } else {
27             for index in 0...25 {
28                 commonCount[index] = min(commonCount[index], thisFrequency[index])
29             }
30         }
31     }
32     
33     for index in 0...25 {
34         while commonCount[index] > 0 {
35             let value = index + 97
36             if let scalar = UnicodeScalar(value) {
37                 let character = Character(scalar)
38                 ans.append("\(character)")
39             }
40             commonCount[index] -= 1
41         }
42     }
43     
44     return ans
45     }
46 }

68ms

 1 class Solution {
 2     func commonChars(_ words: [String]) -> [String] {
 3         var prevDict = [String:Int]()
 4         var currDict = [String:Int]()
 5 
 6         // Get the first word, otherwise return
 7         guard let firstWord = words.first else {
 8             return []
 9         }
10 
11         // Add chars of first word to result
12         for char in firstWord {
13             let char = String(char)
14             if let prevFreq = prevDict[char] {
15                 prevDict[char] = prevFreq + 1
16             }
17             else {
18                 prevDict[char] = 1
19             }
20         }
21 
22         for word in words[1...] {
23             for char in word {
24                 //char is in previous dictionary
25                 //Add to current
26                 let char = String(char)
27                 if let prevFreq = prevDict[char] {
28                     if let currentFreq = currDict[char] {
29                         currDict[char] = currentFreq < prevFreq ? currentFreq + 1 : prevFreq
30                     }
31                     else {
32                         currDict[char] = 1
33                     }
34                 }
35             }
36 
37             //Setup for next iteration
38             prevDict = currDict
39             currDict.removeAll()
40         }
41 
42         var result = [String]()
43         for (char, freq) in prevDict {
44             for _ in 0..<freq {
45                 result.append(char)
46             }
47         }
48 
49         return result
50     }
51 }

72ms

 1 class Solution {
 2     func commonChars(_ A: [String]) -> [String] {
 3         var repeatCount: [Int] = Array.init(repeating: 0, count: 26)
 4         var outPutString = [String]()
 5         let aChar: String = "a"
 6         
 7         var count: Int = 0
 8         for eachString in A {
 9             var onceCount: [Int] = Array.init(repeating: 0, count: 26)
10             for char in eachString {
11                 let acharNUm: Int = aChar.transInToAcsIIInt()
12                 let charNUm: Int = String(char).transInToAcsIIInt()
13                 let counter: Int = charNUm - acharNUm
14                 if count == 0 {
15                     repeatCount[counter] += 1
16                 } else {
17                     onceCount[counter] += 1
18                 }
19             }
20             for index in 0..<26 {
21                 if count != 0 {
22                     repeatCount[index] = min(repeatCount[index], onceCount[index])
23                 }
24             }
25             count += 1
26         }
27         
28         count = 0
29         for eachNum in repeatCount {
30             for _ in 0..<eachNum {
31                 outPutString.append(String(Character(UnicodeScalar(aChar.transInToAcsIIInt() + count)!)))
32             }
33             count += 1
34         }
35         
36         return outPutString;
37     }
38 }
39 
40 
41 
42 extension String {
43     func transInToAcsIIInt() -> Int {
44         var acharNUm: Int = 0
45         for num in self.unicodeScalars {
46             acharNUm = Int(num.value)
47         }
48         
49         return acharNUm
50     }
51 }

76ms

 1 class Solution {
 2     func commonChars(_ A: [String]) -> [String] {
 3         let ref = A[0]
 4         var refDict = [Character: Int]()
 5         for char in ref {
 6             refDict[char, default: 0] += 1
 7         }
 8         
 9         for i in 1..<A.count {
10             let str = A[i]
11             var dict = [Character: Int]()
12             for char in str {
13                 dict[char, default: 0] += 1
14             }
15 
16             for char in refDict.keys {
17                 if let count = dict[char] {
18                     refDict[char] = min(refDict[char]!, count)
19                 } else {
20                     refDict[char] = nil
21                 }
22             }
23         }
24         
25         var result = [String]()
26         for (char, count) in refDict {
27             for _ in 0..<count {
28                 result.append(String(char))
29             }
30         }
31         return result
32     }
33 }

80ms

 1 class Solution {
 2     func commonChars(_ A: [String]) -> [String] {
 3             func f(A: [[Character]], result: [String]) -> [String] {
 4                 if (A.count == 0) { return result }
 5                 var newA = A
 6                 var currentWord = newA.removeFirst().map{ String($0) }
 7                 var i1 = 0
 8                 var res = [String]()
 9                 while i1 < result.count {
10                     let f_char = result[i1]
11                     if let founded_char_index = currentWord.firstIndex(of: f_char) {
12                         res.append(String(f_char))
13                         currentWord.remove(at: founded_char_index)
14                     }
15                     i1 += 1
16                 }
17                 return f(A: newA, result: res)
18             }    
19             var strings = A.map{Array(String($0))}
20             let result = strings.removeFirst().map{ String($0) }
21             return f(A: strings, result: result)
22     }
23 }

Runtime: 88 ms

Memory Usage: 19.7 MB

 1 class Solution {
 2     func commonChars(_ A: [String]) -> [String] {
 3         var n:Int = A.count
 4         var h:[[Int]] = [[Int]](repeating:[Int](repeating:0,count:26),count:n)
 5         for i in 0..<n
 6         {
 7             for j in 0..<A[i].count
 8             {
 9                 h[i][A[i][j].ascii - 97] += 1
10             }
11         }
12         var ans:[String] = [String]()
13         for j in 0..<26
14         {
15             var num:Int = 10000
16             for i in 0..<n
17             {
18                 num = min(h[i][j], num)
19             }
20             var cs:String = String((j + 97).ASCII)
21             for i in 0..<num
22             {
23                 ans.append(cs)
24             }
25         }
26         return ans        
27     }
28 }
29 
30 //String扩展
31 extension String {        
32     //subscript函数可以检索数组中的值
33     //直接按照索引方式截取指定索引的字符
34     subscript (_ i: Int) -> Character {
35         //读取字符
36         get {return self[index(startIndex, offsetBy: i)]}
37     }
38 }
39 
40 //Character扩展 
41 extension Character  
42 {  
43   //转ASCII整数值(定义小写为整数值)
44    var ascii: Int {
45        get {
46            return Int(self.unicodeScalars.first!.value)
47        }       
48     }    
49 }
50 
51 //Int扩展
52 extension Int
53 {
54     //属性：ASCII值(定义大写为字符值)
55     var ASCII:Character 
56     {
57         get {return Character(UnicodeScalar(self)!)}
58     }
59 }

92ms

 1 class Solution {
 2     func commonChars(_ A: [String]) -> [String] {
 3         var results = [String]()
 4         guard A.count > 0 else { return results }
 5         var masterMap = [String : Int]()
 6         for char in A[0] {
 7             let s = String(char)
 8             guard masterMap[s] != nil else {
 9                 masterMap[s] = 1
10                 continue
11             }
12             masterMap[s]! += 1
13         }
14         for i in 1..<A.count {
15             guard masterMap.count > 0 else { return results }
16             var tempMap = [String : Int]()
17             for char in A[i] {
18                 let s = String(char)
19                 guard tempMap[s] != nil else {
20                     tempMap[s] = 1
21                     continue
22                 }
23                 tempMap[s]! += 1
24             }
25             for key in masterMap.keys {
26                 guard let temp = tempMap[key], let master = masterMap[key] else {
27                     masterMap.removeValue(forKey: key)
28                     continue
29                 }
30                 masterMap[key] = min(master, temp)
31             }
32         }
33         for (key, value) in masterMap {
34             for _ in 0..<value {
35                 results.append(key)
36             }
37         }
38         return results
39     }
40 }

100ms

 1 struct CharCounter
 2 {    
 3     var countOf: [ Character : Int ]    
 4     init()
 5     {
 6         self.countOf = [ : ]
 7     }
 8     
 9     mutating func insert( _ char: Character )
10     {
11         if let count: Int = countOf[ char ]
12         {
13             countOf[ char ] = ( count + 1 )
14         }
15         else
16         {
17             countOf[ char ] = 1
18         }
19     }
20     
21     func countOf( _ char: Character ) -> Int
22     {
23         if let count: Int = countOf[ char ]
24         {
25             return count
26         }
27         else
28         {
29             return 0
30         }        
31     }    
32 }
33 
34 class Solution 
35 {    
36     func commonChars( _ strings: [ String ] ) -> [ String ] 
37     {        
38         var charSets: [ CharCounter ] = [ CharCounter ].init(
39             repeating: CharCounter(), 
40             count: strings.count
41         )        
42         var index: Int = 0        
43         while index < strings.count
44         {            
45             let string = strings[ index ]
46             
47             for char in string
48             {
49                 charSets[ index ].insert( char )
50             }            
51             index += 1            
52         }        
53         var result: [ String ] = []
54         
55         for char in charSets[ 0 ].countOf.keys
56         {
57             
58             var minCount: Int = charSets[ 0 ].countOf( char ) 
59             
60             var index: Int = 1
61             while index < charSets.count
62             {                
63                 minCount = min( minCount, charSets[ index ].countOf( char ) )                
64                 index += 1                
65             }
66             
67             if minCount > 0
68             {
69                 for _ in ( 1 ... minCount )
70                 {
71                     result.append( String( char ) )
72                 }
73             }            
74         }        
75         return result        
76     }    
77 }

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