[英]Generating random doable math problems swift
我正在尋找一個返回數學方程的函數,該函數可以在一個腦袋中執行(顯然,這有點主觀,但我不確定該如何表達)。
我想使用+,-,*,/,%和()操作。
目前,我具有此功能:
func createMathString() -> String{
let firstNum = Int(arc4random_uniform(300))
let secNum = Int(arc4random_uniform(300))
let exp = Int(arc4random_uniform(4))
print("\(firstNum) \(self.expressions[exp]) \(secNum)")
return "\(firstNum) \(self.expressions[exp]) \(secNum)"
}
其中self.expression是一個包含+,-,*,/的數組。
該函數返回一個字符串,然后使用該函數對其進行解釋:
let question = createMathString()
let mathExpression = NSExpression(format: question)
let mathValue = mathExpression.expressionValue(with: nil, context: nil) as? Int
我的問題:
1)隨着數字的增加,除法和乘法變得困難
2)我不確定是否必須添加()。 (並非每個問題都會由它們組成,這取決於術語的數量。
3)我希望問題能夠很容易地在某人的腦海中完成,但又不要輕易將隨機數減少到0-50。
我在尋找一種可能的API,但找不到適合我需求的API。
我開始使用Turbo Pascal編程,正如Niklaus Wirth所說: 算法+數據結構=程序 。 您需要定義適合您的程序的數據結構。
首先,一些基本的數據結構。 (快速枚舉比其他語言功能強大得多)
enum MathElement : CustomStringConvertible {
case Integer(value: Int)
case Percentage(value: Int)
case Expression(expression: MathExpression)
var description: String {
switch self {
case .Integer(let value): return "\(value)"
case .Percentage(let percentage): return "\(percentage)%"
case .Expression(let expr): return expr.description
}
}
var nsExpressionFormatString : String {
switch self {
case .Integer(let value): return "\(value).0"
case .Percentage(let percentage): return "\(Double(percentage) / 100)"
case .Expression(let expr): return "(\(expr.description))"
}
}
}
enum MathOperator : String {
case plus = "+"
case minus = "-"
case multiply = "*"
case divide = "/"
static func random() -> MathOperator {
let allMathOperators: [MathOperator] = [.plus, .minus, .multiply, .divide]
let index = Int(arc4random_uniform(UInt32(allMathOperators.count)))
return allMathOperators[index]
}
}
現在的主要課程:
class MathExpression : CustomStringConvertible {
var lhs: MathElement
var rhs: MathElement
var `operator`: MathOperator
init(lhs: MathElement, rhs: MathElement, operator: MathOperator) {
self.lhs = lhs
self.rhs = rhs
self.operator = `operator`
}
var description: String {
var leftString = ""
var rightString = ""
if case .Expression(_) = lhs {
leftString = "(\(lhs))"
} else {
leftString = lhs.description
}
if case .Expression(_) = rhs {
rightString = "(\(rhs))"
} else {
rightString = rhs.description
}
return "\(leftString) \(self.operator.rawValue) \(rightString)"
}
var result : Any? {
let format = "\(lhs.nsExpressionFormatString) \(`operator`.rawValue) \(rhs.nsExpressionFormatString)"
let expr = NSExpression(format: format)
return expr.expressionValue(with: nil, context: nil)
}
static func random() -> MathExpression {
let lhs = MathElement.Integer(value: Int(arc4random_uniform(10)))
let rhs = MathElement.Integer(value: Int(arc4random_uniform(10)))
return MathExpression(lhs: lhs, rhs: rhs, operator: .random())
}
}
用法:
let a = MathExpression(lhs: .Integer(value: 1), rhs: .Integer(value: 2), operator: .divide)
let b = MathExpression(lhs: .Integer(value: 10), rhs: .Percentage(value: 20), operator: .minus)
let c = MathExpression.random()
let d = MathExpression(lhs: .Integer(value: 1), rhs: .Integer(value: 2), operator: .plus)
let e = MathExpression(lhs: .Integer(value: 3), rhs: .Integer(value: 4), operator: .plus)
let f = MathExpression(lhs: .Expression(expression: d), rhs: .Expression(expression: e), operator: .multiply)
let x = MathExpression.random()
let y = MathExpression.random()
let z = MathExpression(lhs: .Expression(expression: x), rhs: .Expression(expression: y), operator: .plus)
print("a: \(a) = \(a.result!)")
print("b: \(b) = \(b.result!)")
print("c: \(c) = \(c.result!)")
print("f: \(f) = \(f.result!)") // the classic (1 + 2) * (3 + 4)
print("z: \(z) = \(z.result!)") // this is completely random
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