好久没写过了,最近在项目中有一个用到数字计算的功能,就想着写下,记下来,以后好歹还能看到,因为之前搜索IOS算式并没有什么方法能够实现比如 1+23/3(3+3) 这种运算,我就想到通过正则的方式去计算,因为算式长度不限,数值不限,所以最简单的方法就是正则了,但是网上又没有这种算法,所以就根据java的正则计算公式,写出来iOS的正则计算公式.
借鉴java代码来源:https://blog.csdn.net/qq_41819893/article/details/127780029
好了废话不多,上主菜:
首先定义下正则,然后定义下需要的运算符
private static let SYMBOL = "\\+|-|\\*|/|\\(|\\)|\\%"
private static let LEFT = "("
private static let RIGHT = ")"
private static let ADD = "+"
private static let MINUS = "-"
private static let TIMES = "*"
private static let DIVISION = "/"
private static let REMAINDER = "%"
private static let LEVEL_01 = 1
private static let LEVEL_02 = 2
private static let LEVEL_HIGH = Int.max
private var stack: [String] = []
private var data: [String] = []
其次就是进行字符串的拆分了
func replaceAllBlank(_ s: String) -> String {
return s.replacingOccurrences(of: "\\s+", with: "", options: .regularExpression)
}
func isNumber(_ s: String) -> Bool {
let pattern = "^[-\\+]?[.\\d]*$"
return s.range(of: pattern, options: .regularExpression) != nil
}
func isSymbol(_ s: String) -> Bool {
return s.range(of: MLC_ReversePolishCalculator.SYMBOL, options: .regularExpression) != nil
}
之后就要将运算的优先级区分下
func calcLevel(_ s: String) -> Int {
if s == MLC_ReversePolishCalculator.ADD || s == MLC_ReversePolishCalculator.MINUS {
return MLC_ReversePolishCalculator.LEVEL_01
} else if s == MLC_ReversePolishCalculator.TIMES || s == MLC_ReversePolishCalculator.DIVISION || s == MLC_ReversePolishCalculator.REMAINDER {
return MLC_ReversePolishCalculator.LEVEL_02
}
return MLC_ReversePolishCalculator.LEVEL_HIGH
}
重点来了啊
func doTheMath(_ s1: String, _ s2: String, _ symbol: String) -> Double {
switch symbol {
case MLC_ReversePolishCalculator.ADD: return Double(s1)! + Double(s2)!
case MLC_ReversePolishCalculator.MINUS: return Double(s1)! - Double(s2)!
case MLC_ReversePolishCalculator.TIMES: return Double(s1)! * Double(s2)!
case MLC_ReversePolishCalculator.DIVISION: return Double(s1)! / Double(s2)!
case MLC_ReversePolishCalculator.REMAINDER: return Double(Double(s1)!.truncatingRemainder(dividingBy: Double(s2)!))
default: return 0
}
}
func run(_ math: String) {
do {
_ = try doCalc(doMatch(math))
} catch {
MLC_Log.log(error, level: 99)
}
}
