[Swift]LeetCode227. 基本计算器 II | Basic Calculator II
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➤微信公众号：山青咏芝（shanqingyongzhi）
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➤GitHub地址：https://github.com/strengthen/LeetCode
➤原文地址：https://www.cnblogs.com/strengthen/p/10204363.html
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Implement a basic calculator to evaluate a simple expression string.
The expression string contains only non-negative integers, +, -, *, /operators and empty spaces . The integer division should truncate toward zero.
Example 1:
Input: "3+2*2" Output: 7
Example 2:
Input: " 3/2 " Output: 1
Example 3:
Input: " 3+5 / 2 " Output: 5
Note:
- You may assume that the given expression is always valid.
- Do not use the
evalbuilt-in library function.
实现一个基本的计算器来计算一个简单的字符串表达式的值。
字符串表达式仅包含非负整数，+， - ，*，/ 四种运算符和空格 。 整数除法仅保留整数部分。
示例 1:
输入: "3+2*2" 输出: 7
示例 2:
输入: " 3/2 " 输出: 1
示例 3:
输入: " 3+5 / 2 " 输出: 5
说明：
- 你可以假设所给定的表达式都是有效的。
- 请不要使用内置的库函数
eval。
116ms
1 class Solution { 2 func calculate(_ s: String) -> Int { 3 var num = 0 4 var sign = "+" 5 var strArr = Array(s) 6 var stack = [Int]() 7 var res = 0 8 9 for i in 0..<strArr.count { 10 if strArr[i] >= "0" && strArr[i] <= "9" { 11 num = num * 10 + Int(String(strArr[i]))! 12 } 13 14 if ((strArr[i] < "0" || strArr[i] > "9") && strArr[i] != " ") || i == strArr.count - 1 { 15 if sign == "+" { 16 stack.append(num) 17 } else if sign == "-" { 18 stack.append(-num) 19 } else if sign == "*" { 20 stack.append(stack.removeLast() * num) 21 } else if sign == "/" { 22 stack.append(stack.removeLast() / num) 23 } 24 25 sign = String(strArr[i]) 26 num = 0 27 } 28 } 29 30 31 for i in stack { 32 res += i 33 } 34 35 return res 36 } 37 }
124ms
1 class Solution { 2 func calculate(_ s: String) -> Int { 3 var stack = [Int]() 4 var str = Array(s+"+") 5 6 var num = 0 7 var sign: Character = "+" 8 9 for char in str { 10 if char >= "0" && char <= "9" { 11 num = num * 10 + Int(String(char))! 12 } else if operators.contains(char) { 13 if sign == "+" || sign == "-"{ 14 stack.append((sign == "-" ? -1 : 1) * num) 15 } else if sign == "*" || sign == "/" { 16 let n = stack.removeLast() 17 stack.append(sign == "*" ? n * num : n / num) 18 } 19 num = 0 20 sign = char 21 } 22 } 23 return stack.reduce(0, +) 24 } 25 26 let operators = Set<Character>(["+", "-", "*", "/"]) 27 }
140ms
1 class Solution { 2 func calculate(_ s: String) -> Int { 3 var stack = [Int]() 4 var str = Array(s+"+") 5 6 var num = 0 7 var sign: Character = "+" 8 9 for char in str { 10 if operands.contains(char) { 11 num = num * 10 + Int(String(char))! 12 } else if operators.contains(char) { 13 if sign == "+" || sign == "-"{ 14 stack.append((sign == "-" ? -1 : 1) * num) 15 } else if sign == "*" || sign == "/" { 16 let n = stack.removeLast() 17 stack.append(sign == "*" ? n * num : n / num) 18 } 19 num = 0 20 sign = char 21 } 22 } 23 return stack.reduce(0, +) 24 } 25 26 let operators = Set<Character>(["+", "-", "*", "/"]) 27 let operands = Set<Character>(["0", "1", "2", "3", "4", "5", "6", "7", "8", "9"]) 28 }
228ms
1 class Solution { 2 func calculate(_ s: String) -> Int { 3 var nums: [Int] = [] 4 var operations: [Character] = [] 5 var preNum = "" 6 for char in s { 7 if let _ = Int(String(char)) { 8 preNum += String(char) 9 } else { 10 if preNum != "" { 11 nums.append(Int(preNum)!) 12 preNum = "" 13 } 14 15 if !operations.isEmpty { 16 let operation = operations[operations.count - 1] 17 if nums.count > operations.count && (operation == "*" || operation == "/") { 18 let num2 = nums.popLast()! 19 let num1 = nums.popLast()! 20 if operation == "*" { 21 let num = num1 * num2 22 nums.append(num) 23 } else if operation == "/" { 24 let num = num1 / num2 25 nums.append(num) 26 } 27 28 operations.removeLast() 29 } 30 } 31 32 33 if char != " " { 34 operations.append(char) 35 } 36 } 37 } 38 39 if preNum != "" { 40 nums.append(Int(preNum)!) 41 } 42 43 if !operations.isEmpty && operations.last == "/" || operations.last == "*" { 44 let operation = operations.popLast()! 45 let num2 = nums.popLast()! 46 let num1 = nums.popLast()! 47 if operation == "*" { 48 nums.append(num1 * num2) 49 } else if operation == "/" { 50 nums.append(num1 / num2) 51 } 52 } 53 54 nums.reverse() 55 for operation in operations { 56 let num1 = nums.popLast()! 57 let num2 = nums.popLast()! 58 if operation == "+" { 59 nums.append(num1 + num2) 60 } else if operation == "-" { 61 nums.append(num1 - num2) 62 } else if operation == "*" { 63 nums.append(num1 * num2) 64 } else if operation == "/" { 65 nums.append(num1 / num2) 66 } 67 } 68 69 return nums.isEmpty ? 0 : nums[0] 70 } 71 }
548ms
1 class Solution { 2 func calculate(_ s: String) -> Int { 3 var numStack = [Int]() 4 var opeStack = [String]() 5 let sArr = Array(s) 6 let nums = "0123456789" 7 let opes = "+-*/" 8 9 var i = 0 10 while i < sArr.count { 11 let c = sArr[i] 12 if nums.contains(c) { 13 var tmp = 0 14 while i < sArr.count && nums.contains(sArr[i]) { 15 tmp = tmp * 10 + Int(String(sArr[i]))! 16 i += 1 17 } 18 if let ope = opeStack.last, ope == "*" || ope == "/" { 19 let last = numStack.removeLast() 20 opeStack.removeLast() 21 if ope == "*" { 22 tmp *= last 23 }else if ope == "/" { 24 tmp = last / tmp 25 } 26 27 } 28 numStack.append(tmp) 29 i -= 1 30 }else if opes.contains(c) { 31 opeStack.append(String(c)) 32 } 33 34 i += 1 35 } 36 37 var res = numStack.first ?? 0 38 39 for i in 0..<opeStack.count { 40 let ope = opeStack[i] 41 if ope == "+" { 42 res += numStack[i+1] 43 }else if ope == "-" { 44 res -= numStack[i+1] 45 } 46 } 47 return res 48 } 49 }
