[Swift]LeetCode8. 字符串轉整數 (atoi) | String to Integer (atoi)
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➤微信公衆號：山青詠芝（shanqingyongzhi）
➤博客園地址：山青詠芝（https://www.cnblogs.com/strengthen/）
➤GitHub地址：https://github.com/strengthen/LeetCode
➤原文地址：http://www.javashuo.com/article/p-yezyumjn-me.html
➤若是連接不是山青詠芝的博客園地址，則多是爬取做者的文章。
➤原文已修改更新！強烈建議點擊原文地址閱讀！支持做者！支持原創！
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Implement atoi which converts a string to an integer.git
The function first discards as many whitespace characters as necessary until the first non-whitespace character is found. Then, starting from this character, takes an optional initial plus or minus sign followed by as many numerical digits as possible, and interprets them as a numerical value.github
The string can contain additional characters after those that form the integral number, which are ignored and have no effect on the behavior of this function.微信
If the first sequence of non-whitespace characters in str is not a valid integral number, or if no such sequence exists because either str is empty or it contains only whitespace characters, no conversion is performed.app
If no valid conversion could be performed, a zero value is returned.ide
Note:函數
- Only the space character
' 'is considered as whitespace character. - Assume we are dealing with an environment which could only store integers within the 32-bit signed integer range: [−231, 231 − 1]. If the numerical value is out of the range of representable values, INT_MAX (231 − 1) or INT_MIN (−231) is returned.
Example 1:post
Input: "42" Output: 42
Example 2:this
Input: " -42" Output: -42 Explanation: The first non-whitespace character is '-', which is the minus sign. Then take as many numerical digits as possible, which gets 42.
Example 3:spa
Input: "4193 with words" Output: 4193 Explanation: Conversion stops at digit '3' as the next character is not a numerical digit.
Example 4:
Input: "words and 987" Output: 0 Explanation: The first non-whitespace character is 'w', which is not a numerical digit or a +/- sign. Therefore no valid conversion could be performed.
Example 5:
Input: "-91283472332" Output: -2147483648 Explanation: The number "-91283472332" is out of the range of a 32-bit signed integer. Thefore INT_MIN (−231) is returned.
實現 atoi，將字符串轉爲整數。
該函數首先根據須要丟棄任意多的空格字符，直到找到第一個非空格字符爲止。若是第一個非空字符是正號或負號，選取該符號，並將其與後面儘量多的連續的數字組合起來，這部分字符即爲整數的值。若是第一個非空字符是數字，則直接將其與以後連續的數字字符組合起來，造成整數。
字符串能夠在造成整數的字符後面包括多餘的字符，這些字符能夠被忽略，它們對於函數沒有影響。
當字符串中的第一個非空字符序列不是個有效的整數；或字符串爲空；或字符串僅包含空白字符時，則不進行轉換。
若函數不能執行有效的轉換，返回 0。
說明：
假設咱們的環境只能存儲 32 位有符號整數，其數值範圍是 [−231, 231 − 1]。若是數值超過可表示的範圍，則返回 INT_MAX (231 − 1) 或 INT_MIN (−231) 。
示例 1:
輸入: "42" 輸出: 42
示例 2:
輸入: " -42" 輸出: -42 解釋: 第一個非空白字符爲 '-', 它是一個負號。 咱們儘量將負號與後面全部連續出現的數字組合起來，最後獲得 -42 。
示例 3:
輸入: "4193 with words" 輸出: 4193 解釋: 轉換截止於數字 '3' ，由於它的下一個字符不爲數字。
示例 4:
輸入: "words and 987"
輸出: 0
解釋: 第一個非空字符是 'w', 但它不是數字或正、負號。
所以沒法執行有效的轉換。
示例 5:
輸入: "-91283472332" 輸出: -2147483648 解釋: 數字 "-91283472332" 超過 32 位有符號整數範圍。 所以返回 INT_MIN (−231) 。
44ms
1 class Solution { 2 func myAtoi(_ str: String) -> Int { 3 //除去先後空格 4 var str = str.trimmingCharacters(in: .whitespaces) 5 if str.isEmpty {return 0} 6 var sign:Int = 1,base:Int = 0,i:Int = 0,n:Int = str.count 7 while(i < n && str.charAt(i) == " ") 8 { 9 i += 1 10 } 11 if str.charAt(i) == "+" || str.charAt(i) == "-" 12 { 13 sign = (str.charAt(i++) == "+") ? 1 : -1 14 } 15 //ASCII: '0'爲48 '9'爲57 16 while(i < n && str.toInt(i) >= 48 && str.toInt(i) <= 57) 17 { 18 if base > Int32.max / 10 || (base == Int32.max / 10 && str.toInt(i) - 48 > 7) 19 { 20 return (sign == 1) ? Int(Int32.max) : Int(Int32.min) 21 } 22 base = 10 * base + (str.toInt(i++) - 48) 23 } 24 return base * sign 25 } 26 } 27 28 extension String { 29 //獲取指定索引位置的字符，返回爲字符串形式 30 func charAt(_ num:Int) -> String 31 { 32 guard num < self.count else { 33 assertionFailure("Index out of range!") 34 return String() 35 } 36 let index = self.index(self.startIndex,offsetBy: num) 37 return String(self[index]) 38 } 39 40 //獲取指定索引位置字符的ASCII整數值 41 func toInt(_ num:Int) -> Int 42 { 43 guard num < self.count else { 44 assertionFailure("Index out of range!") 45 return 0 46 } 47 var number:Int = Int() 48 for scalar in charAt(num).unicodeScalars 49 { 50 number = Int(scalar.value) 51 } 52 return number 53 } 54 } 55 56 /*擴展Int類，實現自增++*/ 57 extension Int{ 58 //後綴++:先執行表達式後再自增 59 static postfix func ++(num:inout Int) -> Int { 60 //輸入輸出參數num 61 let temp = num 62 //num加1 63 num += 1 64 //返回加1前的數值 65 return temp 66 } 67 }
16ms
1 class Solution { 2 func myAtoi(_ str: String) -> Int { 3 let stringLength = str.count 4 var index = 0 5 6 var result = 0 7 let base = 10 8 var sign: Int? = nil // 1 if positive, -1 if negative, nil if not determined 9 var integralPartStarted = false 10 11 while index < stringLength { 12 let character = str[str.index(str.startIndex, offsetBy: index)] 13 let isWhitespaceCharacter = self.isWhitespace(character) 14 let isNumericCharacter = self.isNumeric(character) 15 let numericValue = self.numericValue(character) 16 17 index += 1 18 19 if integralPartStarted == false { 20 if isWhitespaceCharacter { 21 continue 22 } else if let _sign = self.sign(character) { 23 sign = _sign 24 integralPartStarted = true 25 continue 26 } else if isNumericCharacter { 27 sign = 1 28 integralPartStarted = true 29 } else { 30 return 0 31 } 32 } 33 34 if integralPartStarted { 35 if let numericValue = numericValue { 36 let nextResult = result * base + numericValue 37 if nextResult > Int32.max { 38 return (sign ?? 1 > 0) ? Int(Int32.max) : Int(Int32.min) 39 } else { 40 result = nextResult 41 } 42 } else { 43 return result * (sign ?? 1) 44 } 45 } 46 } 47 48 return result * (sign ?? 1) 49 } 50 51 func isNumeric(_ character: Character) -> Bool { 52 return character >= "0" && character <= "9" 53 } 54 55 let unicodeScalar0 = UnicodeScalar("0").value 56 57 // returns the numeric value of the character, returns nil if the character is not a valid numeric character 58 func numericValue(_ character: Character) -> Int? { 59 guard isNumeric(character) else { 60 return nil 61 } 62 63 return Int(character.unicodeScalars.first!.value - unicodeScalar0) 64 } 65 66 func isWhitespace(_ character: Character) -> Bool { 67 return character == " " 68 } 69 70 // returns -1 if negative, +1 if positive, nil if none 71 func sign(_ character: Character) -> Int? { 72 if character == "+" { 73 return 1 74 } else if character == "-" { 75 return -1 76 } else { 77 return nil 78 } 79 } 80 }
20ms
1 class Solution { 2 func myAtoi(_ str: String) -> Int { 3 var result: Int64 = 0 4 var sign: Int64 = 1 5 var strArr = Array(str) 6 7 strArr = stripLeading(chars: strArr, toRemove: " ") 8 9 var n = strArr.count 10 if (n == 0) { 11 return 0 12 } 13 14 if (strArr[0] == Character("-")) { 15 sign = -1 16 strArr.remove(at: 0) 17 } 18 else if (strArr[0] == Character("+")) { 19 sign = 1 20 strArr.remove(at: 0) 21 } 22 23 strArr = stripLeading(chars: strArr, toRemove: "0") 24 25 n = strArr.count 26 if (n == 0) { 27 return 0 28 } 29 30 for i in 0..<n { 31 32 var lastDigit = convertToInt(strArr[i]) 33 if (lastDigit == -1) { 34 return Int(sign*result) 35 } 36 37 result = result*10 + Int64(lastDigit) 38 39 if !isWithinInt32Range(sign*result) { 40 return sign > 0 ? Int(Int32.max) : Int(Int32.min) 41 } 42 } 43 44 return Int(sign*result) 45 } 46 47 private func isWithinInt32Range(_ value: Int64) -> Bool { 48 return value > 0 ? value < Int32.max : value > Int32.min 49 } 50 51 private func convertToInt(_ c: Character) -> Int { 52 switch c { 53 case "0": return 0 54 case "1": return 1 55 case "2": return 2 56 case "3": return 3 57 case "4": return 4 58 case "5": return 5 59 case "6": return 6 60 case "7": return 7 61 case "8": return 8 62 case "9": return 9 63 default: return -1 64 } 65 } 66 67 private func stripWhiteSpace(_ chars: [Character]) -> [Character] { 68 var n: Int = chars.count 69 var i: Int = 0 70 for i in 0..<n { 71 if chars[i] != " " { 72 return Array(chars[i...n-1]) 73 } 74 } 75 76 return [] 77 } 78 79 private func stripLeading(chars: [Character], toRemove c: Character) -> [Character] { 80 var n: Int = chars.count 81 var i: Int = 0 82 for i in 0..<n { 83 if chars[i] != c { 84 return Array(chars[i...n-1]) 85 } 86 } 87 88 return [] 89 } 90 }
20ms
1 class Solution { 2 func myAtoi(_ str: String) -> Int { 3 if str.isEmpty { 4 return 0 5 } 6 7 let ＋: Int8 = 43 8 let －: Int8 = 45 9 let ascii0: Int8 = 48 10 let ascii9: Int8 = 57 11 let space: Int8 = 32 12 13 14 var sign: Int = 1 15 16 var result: Int = 0 17 18 let chars = str.utf8CString 19 20 var i: Int = 0 21 22 while chars[i] == space { 23 i += 1 24 } 25 26 if chars[i] == ＋ || chars[i] == － { 27 sign = chars[i] == － ? -1 : 1 28 i += 1 29 } 30 31 while i < chars.count - 1, ascii0...ascii9 ~= chars[i] { 32 33 if result > Int32.max / 10 || (result == Int32.max / 10 && Int(chars[i] - ascii0) > 7) { 34 return sign == 1 ? Int(Int32.max) : Int(Int32.min) 35 } 36 37 result = result * 10 + Int(chars[i] - ascii0) 38 i += 1 39 } 40 41 return result * sign 42 } 43 }
24ms
1 class Solution { 2 func myAtoi(_ str: String) -> Int { 3 var result = 0 4 let arr = Array(str) 5 var sign = 1 6 7 var i = 0 8 while i < arr.count { 9 if arr[i] != " " { 10 break 11 } 12 i += 1 13 } 14 15 if i >= arr.count { 16 return 0 17 } 18 19 if arr[i] == "-" { 20 sign = -1 21 i += 1 22 } else if arr[i] == "+" { 23 i += 1 24 } 25 26 while i < arr.count { 27 let c = arr[i] 28 switch c { 29 case "0"..."9": 30 result = result * 10 + Int(String(c))! 31 if sign == 1 && result > Int32.max { 32 return Int(Int32.max) 33 } 34 if sign == -1 && (sign * result) < Int32.min { 35 return Int(Int32.min) 36 } 37 default: 38 return sign * result 39 } 40 i += 1 41 } 42 43 44 return sign * result 45 } 46 }
28ms
1 class Solution { 2 func myAtoi(_ str: String) -> Int { 3 let chars = str.map {String($0)} 4 var first = true 5 var minus = false 6 var result = 0 7 for char in chars { 8 if first { 9 if char == " " { 10 continue 11 } else if char == "-" { 12 minus = true 13 first = false 14 } else if char == "+" { 15 first = false 16 } else if let number = getNumber(char: char) { 17 result = number 18 first = false 19 } else { 20 return 0 21 } 22 } else { 23 if let number = getNumber(char: char) { 24 result = result * 10 + number 25 if result > Int32.max { 26 return minus ? Int(Int32.min) : Int(Int32.max) 27 } 28 } else { 29 break 30 } 31 } 32 } 33 if minus { 34 result = -result 35 } 36 37 return result 38 } 39 40 func getNumber(char: String) -> Int? { 41 guard let number = Int(char) else { 42 return nil 43 } 44 return number 45 } 46 }
28ms
1 class Solution { 2 let intTable: [Character: Int] = ["0": 0, "1": 1, "2": 2, "3": 3, "4": 4, "5": 5, "6": 6, "7": 7, "8": 8, "9": 9] 3 func myAtoi(_ str: String) -> Int { 4 var minus = false 5 var digits: [Int] = [] 6 var start = false 7 for s in str { 8 if !start { 9 if s == " " { 10 continue 11 } else if s == "-" { 12 minus = true 13 start = true 14 } else if s == "+" { 15 start = true 16 } else if let i = intTable[s] { 17 start = true 18 digits.append(i) 19 } else { 20 return 0 21 } 22 } else { 23 if let i = intTable[s] { 24 digits.append(i) 25 } else { 26 break 27 } 28 } 29 } 30 if digits.count == 0 { 31 return 0 32 } 33 34 var headZero = true 35 digits = digits.filter({ v in 36 if v != 0 { 37 headZero = false 38 } 39 return !headZero 40 }) 41 let intMax = Int(pow(Double(2), Double(31))) - 1 42 let intMin = -Int(pow(Double(2), Double(31))) 43 var overflow = false 44 var res = digits.reversed().enumerated().reduce(0) { (r, arg1) -> Int in 45 let (i, v) = arg1 46 if pow(10, Double(i)) > pow(2, 32) { 47 overflow = true 48 return 0 49 } 50 return r + Int(pow(10, Double(i))) * v 51 } 52 if overflow { return minus ? intMin : intMax } 53 if minus { res = -res } 54 55 if res > intMax { 56 return intMax 57 } else if res < intMin { 58 return intMin 59 } 60 61 return res 62 } 63 }
32ms
1 class Solution { 2 func myAtoi(_ str:String) -> Int { 3 4 let negative = 45, posiz = 43, empty = 32 5 6 let nums = str.unicodeScalars.map { Int($0.value) } 7 8 let zero2nine = 48...57 9 10 var result = -1 11 12 var fuhao = -1 13 14 for i in 0..<nums.count { 15 16 let value = nums[i] 17 18 if zero2nine.contains(value) { 19 20 let num = value - 48 21 22 if fuhao == 0 && result > (2147483648 - num)/10 { 23 24 return -2147483648 25 } 26 27 if fuhao != 0 && result > (2147483647 - num)/10 { 28 29 return 2147483647 30 } 31 32 result = (result == -1 ? 0 : result) * 10 + value - 48 33 34 continue 35 } 36 37 if value == empty || value == negative || value == posiz { 38 39 if result == -1 && fuhao == -1 { 40 41 if value == negative { 42 43 fuhao = 0 44 } 45 46 if value == posiz { 47 48 fuhao = 1 49 } 50 51 continue 52 } 53 } 54 55 break 56 } 57 58 if result == -1 { 59 60 return 0 61 } 62 63 if fuhao == -1 || fuhao == 1 { 64 65 return min(2147483647, result) 66 } 67 else { 68 69 return max(-2147483648, -1 * result) 70 } 71 } 72 }
32ms
1 class Solution { 2 func isDigit(_ c: Character) -> Bool { 3 return c >= "0" && c <= "9" 4 } 5 6 func myAtoi(_ str: String) -> Int { 7 var positive: Bool = true 8 var started: Bool = false 9 var number: Int = 0 10 11 for index in str.characters.indices { 12 let char = str[index] 13 if started { 14 if isDigit(char) { 15 let multiplied = number.multipliedReportingOverflow(by: 10) 16 if multiplied.1 { 17 return positive ? Int(Int32.max) : Int(Int32.min) 18 } 19 20 let added = multiplied.0.addingReportingOverflow(Int(String(char))!) 21 if added.1 { 22 return positive ? Int(Int32.max) : Int(Int32.min) 23 } 24 25 number = added.0 26 continue 27 } 28 29 break 30 31 } else { 32 if char == " " { 33 continue 34 } 35 36 if char == "-" { 37 positive = false 38 started = true 39 continue 40 } 41 42 if char == "+" { 43 positive = true 44 started = true 45 continue 46 } 47 48 if isDigit(char) { 49 started = true 50 number = Int(String(char))! 51 continue 52 } 53 54 break 55 } 56 } 57 58 let result = positive ? number : number * -1 59 if result > Int32.max { 60 return Int(Int32.max) 61 } 62 63 if result < Int32.min { 64 return Int(Int32.min) 65 } 66 67 return result 68 69 } 70 }
36ms
1 class Solution { 2 func myAtoi(_ str: String) -> Int { 3 4 var strs = [Character]() 5 var count = 0 6 for scalars in str.unicodeScalars { 7 if 48 <= scalars.value && scalars.value < 58 { 8 let foo = UnicodeScalar(scalars.value) 9 strs.append(Character(foo!)) 10 } else if scalars.value == 45 || scalars.value == 43 { 11 if strs.count == 0 { 12 let foo = UnicodeScalar(scalars.value) 13 strs.append(Character(foo!)) 14 } else { 15 break; 16 } 17 } else if scalars.value == 32 { 18 if strs.count > 0 { 19 break; 20 } 21 } else { 22 if count == 0 { 23 return 0 24 } 25 break; 26 } 27 count += 1 28 } 29 let temp = String(strs) 30 let res = Double(temp) ?? 0 31 32 if res < Double(Int32.min) { 33 return Int(Int32.min) 34 } else if res > Double(Int32.max) { 35 return Int(Int32.max) 36 } else { 37 return Int(temp) ?? 0 38 } 39 } 40 }
36ms
1 class Solution { 2 func myAtoi(_ str: String) -> Int { 3 var foundNumber = false 4 var result: Int64 = 0 5 var sign: Int64 = 1 6 for char in str { 7 if char == Character(" ") { 8 if !foundNumber { continue } else { break } 9 } 10 if "-+".contains(String(char)) { 11 if foundNumber { break } 12 if char == Character("-") { 13 sign = -1 14 } 15 foundNumber = true 16 continue 17 } 18 guard let digit = Int64(String(char)) else { break } 19 foundNumber = true 20 result = result * 10 + digit 21 if result * sign > Int32.max { return Int(Int32.max) } 22 if result * sign < Int32.min { return Int(Int32.min) } 23 } 24 return Int(result * sign) 25 } 26 }
40ms
1 class Solution{ 2 func myAtoi(_ str: String) -> Int { 3 var numberStr = "" 4 var number = 0 5 for character in str{ 6 if character == " " ,numberStr.isEmpty{ 7 continue 8 } 9 else if Int(String(character)) != nil{ 10 numberStr.append(character) 11 } 12 else if (character == "+" || character == "-"),numberStr.isEmpty{ 13 numberStr.append(character) 14 } 15 else{ 16 break 17 } 18 19 } 20 if let num = Int(numberStr){ 21 if num > Int32.max{ 22 number = Int(Int32.max) 23 } 24 else if num < Int32.min{ 25 number = Int(Int32.min) 26 } 27 else{ 28 number = num 29 } 30 } 31 else if numberStr.count > 1{ 32 if numberStr.first == "-"{ 33 number = Int(Int32.min) 34 } 35 else{ 36 number = Int(Int32.max) 37 } 38 39 } 40 41 return number 42 } 43 }
40ms
1 class Solution { 2 func myAtoi(_ str: String) -> Int { 3 4 // var str = str.replacingOccurrences(of:" ", with: "") 5 6 var minus = 1 7 var isNum = false 8 var num = 0 9 var isSysmbol = false 10 var isFirstcharacter = false 11 12 for ch in str { 13 14 15 if isFirstcharacter == true && Int(String(ch)) == nil { 16 17 return num 18 } 19 20 21 if ch == "-" { 22 23 minus = -1 24 isFirstcharacter = true 25 continue 26 } 27 28 if ch == "+" { 29 30 isFirstcharacter = true 31 continue 32 33 } 34 35 if ch == " " { 36 37 continue 38 } 39 40 if let value = Int(String(ch)) { 41 42 isFirstcharacter = true 43 num = num * 10 + (value * minus) 44 45 } else { 46 47 return num 48 } 49 50 if num > Int32.max { 51 52 return Int(Int32.max) 53 } 54 55 if num < Int32.min { 56 57 return Int(Int32.min) 58 } 59 60 } 61 62 return num 63 } 64 }
44ms
1 class Solution { 2 func myAtoi(_ str: String) -> Int { 3 let chars = [Character](str) 4 5 var result = 0 6 var sign = 0 7 var isPrefix = true 8 var index = 0 9 for char in chars { 10 // 1. 先判斷字符串前面的空格 11 if char == " " && isPrefix { 12 continue 13 } 14 15 isPrefix = false 16 17 // 2. 判斷正負號 18 if char == "+" || char == "-" { 19 if sign != 0 || index != 0 { 20 break 21 } 22 sign = char == "+" ? 1 : -1 23 continue 24 } 25 26 // 3. 判斷合理的值 27 if char >= "0" && char <= "9" { 28 let charValue = Int(String(char))! 29 30 // 3.1 大於最大值 31 if sign >= 0 && result > ((Int(Int32.max) - charValue) / 10) { 32 return Int(Int32.max) 33 } 34 35 // 3.2 小於最小值 36 if sign == -1 && -result < (Int(Int32.min) + charValue) / 10 { 37 return Int(Int32.min) 38 } 39 40 // 3.3 正常值 41 result = result * 10 + charValue 42 } else { 43 break 44 } 45 index += 1 46 } 47 48 sign = sign == 0 ? 1 : sign 49 50 return result * sign 51 52 53 } 54 }
44ms
1 class Solution { 2 func myAtoi(_ str: String) -> Int { 3 let int_max = 2147483647 4 let int_min = -2147483648 5 6 var asd = Array(str.trimmingCharacters(in: .whitespaces)) 7 if asd.isEmpty { 8 return 0 9 } 10 var flag = 1 11 var result = 0 12 let firstChar = String(asd[0]) 13 if firstChar == "" { 14 return 0 15 } else if firstChar == "-" { 16 flag = -1 17 } else if firstChar == "+" { 18 flag = 1 19 } else if let number = Int(firstChar) { 20 result += number 21 } else { 22 return 0 23 } 24 25 var m = 1 26 while m < asd.count { 27 if let number = Int(String(asd[m])) { 28 print(result) 29 result = result * 10 + number 30 m += 1 31 if result >= int_max { 32 if flag == 1 { 33 return int_max 34 } else if result > int_max && flag == -1 { 35 return int_min 36 } 37 } 38 } else { 39 break 40 } 41 } 42 return flag * result 43 } 44 45 }
48ms
1 class Solution { 2 func myAtoi(_ str: String) -> Int { 3 4 if str.isEmpty { 5 return 0 6 } 7 8 func isNumber(_ character: UInt32) -> Bool{ 9 //斷定數字 10 if character >= 48 && character <= 57 { 11 return true 12 } 13 return false 14 } 15 16 //去掉空格 17 let whitespace = NSCharacterSet.whitespaces 18 let noWhitespaceStr = str.trimmingCharacters(in: whitespace) 19 20 var result = 0 21 var sign = 1 22 for (index,scalar) in noWhitespaceStr.unicodeScalars.enumerated() { 23 if isNumber(scalar.value) || (scalar.value == 45 && index == 0) { 24 //若是第一位是字符 - 則標識爲負數 25 if scalar.value == 45 && index == 0 { 26 sign = -1 27 continue 28 } 29 30 //當前結果大於最大值除以10 31 if result > Int32.max / 10 || (result == Int32.max / 10 && Int(String(scalar))! > 7) { 32 return sign == 1 ? Int(Int32.max) : Int(Int32.min) 33 } 34 35 result = result * 10 + Int(String(scalar))! 36 }else if scalar.value == 43 && index == 0{ 37 continue 38 }else{ 39 break 40 } 41 } 42 43 return result * sign 44 } 45 }
56ms
1 class Solution { 2 func myAtoi(_ str: String) -> Int { 3 4 let arr: [String] = ["0","1","2","3","4","5","6","7","8","9"] 5 var result: Int = 0 6 7 var numbers: [String] = [] 8 for char in str { 9 let temp: String = String.init(char) 10 numbers.append(temp) 11 } 12 13 var flag: Int = 1 14 var pos: Int = -1 15 var haha: Bool = false //表示是否出現了第一個有效的符號 16 17 // 1.首先第一個非空字符字符爲 數字或正、負號。 18 for i in 0..<numbers.count { 19 20 if (numbers[i] == " ") && pos == -1 { 21 continue 22 }else { 23 pos = i 24 } 25 if (numbers[i] == "-" || numbers[i] == "+") && !haha{ 26 flag = (numbers[i] == "+") ? 1 : -1 27 haha = true 28 continue 29 }else if (arr .contains(numbers[i])) { 30 haha = true 31 result = result*10 + Int(numbers[i])! 32 if result > Int32.max && flag == 1{ 33 result = Int(Int32.max) 34 return result 35 }else if result*flag <= Int32.min && flag == -1{ 36 result = Int(Int32.min) 37 return result 38 } 39 }else { 40 break 41 } 42 } 43 return result * flag 44 } 45 }
60ms
1 class Solution { 2 func myAtoi(_ str: String) -> Int { 3 var resultInt:Int = 0 4 var charArray = [Character]() 5 var isBegin:Bool = true 6 var isNegative:Int32 = 1 7 for charAtoi in str.unicodeScalars { 8 let charInt = Int32(charAtoi.value) 9 if (charInt == 32 && isBegin){ 10 continue 11 } else { 12 if (((charInt == 43 || charInt == 45) && isBegin) || (charInt >= 48 && charInt <= 57)){ 13 isBegin = false 14 if charInt == 45 { 15 isNegative = -1 16 } 17 if (charInt >= 48 && charInt <= 57) { 18 if charArray.count > 8 { 19 let currentInt = Int32(String(charArray))! * isNegative 20 print(currentInt) 21 if (currentInt > Int32.max / 10 || (currentInt == Int32.max / 10 && charInt >= 55)) { 22 return Int(Int32.max) 23 } 24 if (currentInt < Int32.min / 10 || (currentInt == Int32.min / 10 && charInt >= 56)) { 25 return Int(Int32.min) 26 } 27 } 28 charArray.append(Character(UnicodeScalar(charAtoi))) 29 } 30 } else { 31 break 32 } 33 } 34 } 35 if charArray.count > 0 { 36 resultInt = Int(String(charArray))! * Int(isNegative) 37 } 38 return resultInt 39 } 40 }
60ms
1 class Solution { 2 func myAtoi(_ str: String) -> Int { 3 var chars = Array(str.trimmingCharacters(in: .whitespaces)) 4 guard chars.count > 0 else { return 0 } 5 let validCharacters = ["-", "+", "0", "1", "2", "3", "4", "5", "6", "7", "8", "9"].map({Character($0)}) 6 guard validCharacters.contains(chars.first!) else { return 0 } 7 chars.filter({validCharacters.contains($0)}) 8 var sign = chars.first == "-" ? -1 : 1 9 if chars.first == "-" || chars.first == "+" { 10 chars.removeFirst() 11 } 12 var intStr = "" 13 for c in chars { 14 if let _ = Int(String(c)) { 15 intStr.append(c) 16 } else { 17 print(c) 18 break 19 } 20 } 21 let sol = (Int(intStr) ?? (intStr.isEmpty ? 0 : sign == -1 ? Int(Int32.max) + 1 : Int(Int32.max))) * sign 22 23 return sign == -1 ? Int(Int32.min) < sol ? sol : Int(Int32.min) : Int(Int32.max) > sol ? sol : Int(Int32.max) 24 } 25 }
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