ios 在 Swift 中如何知道一个数字是奇数还是偶数？
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How to know if a number is odd or even in Swift?
提问by Asif Bilal
I have an array of numbers typed Int.
我输入了一个数字数组Int。
I want to loop through this array and determine if each number is odd or even.
我想遍历这个数组并确定每个数字是奇数还是偶数。
How can I determine if a number is odd or even in Swift?
如何确定一个数字在 Swift 中是奇数还是偶数？
回答by Charith Nidarsha
var myArray = [23, 54, 51, 98, 54, 23, 32];
for myInt: Int in myArray{
if myInt % 2 == 0 {
println("\(myInt) is even number")
} else {
println("\(myInt) is odd number")
}
}
回答by num8er
Use the %Remainder Operator(aka the Modulo Operator) to check if a number is even:
使用%余数运算符（又名模运算符）检查数字是否为偶数：
if yourNumber % 2 == 0 {
// Even Number
} else {
// Odd Number
}
or, use remainder(dividingBy:)to make the same check:
或者，用于remainder(dividingBy:)进行相同的检查：
if yourNumber.remainder(dividingBy: 2) == 0 {
// Even Number
} else {
// Odd Number
}
回答by pkamb
Swift 5 adds the function isMultiple(of:)to the BinaryIntegerprotocol.
Swift 5 将该功能添加isMultiple(of:)到BinaryInteger协议中。
let even = binaryInteger.isMultiple(of: 2)
let odd = !binaryInteger.isMultiple(of: 2)
This function can be used in place of %for odd/even checks.
此函数可用于代替%奇数/偶数检查。
This function was added via the Swift Evolution process:
此功能是通过 Swift Evolution 过程添加的：
- Preliminary Discussion in Swift Forum
- Swift Evolution Proposal
- Accepted Swift Evolution Implementation
Notably, isEvenand isOddwere proposed but notaccepted in the same review:
值得注意的是，isEven和isOdd被提出，但不是在同一个评审接受的：
Given the addition of
isMultiple(of:), the Core Team feels thatisEvenandisOddoffer no substantial advantages overisMultiple(of: 2).Therefore, the proposal is accepted with modifications.
isMultiple(of:)is accepted butisEvenandisOddare rejected.
鉴于添加
isMultiple(of:)，核心团队认为isEven并isOdd没有提供比isMultiple(of: 2).因此，该提案经修改后被接受。
isMultiple(of:)被接受，但isEven和isOdd被拒绝。
If desired, those methods can be added easily through extension:
如果需要，可以通过扩展轻松添加这些方法：
extension BinaryInteger {
var isEven: Bool { isMultiple(of: 2) }
var isOdd: Bool { !isEven }
}
回答by pkamb
"Parity" is the name for the mathematical concept of Odd and Even:
“Parity”是奇数和偶数的数学概念的名称：
You can extend the Swift BinaryIntegerprotocol to include a parityenumeration value:
您可以扩展 SwiftBinaryInteger协议以包含parity枚举值：
enum Parity {
case even, odd
init<T>(_ integer: T) where T : BinaryInteger {
self = integer.isMultiple(of: 2) ? .even : .odd
}
}
extension BinaryInteger {
var parity: Parity { Parity(self) }
}
which enables you to switchon an integer and elegantly handle the two cases:
这使您能够switch使用整数并优雅地处理两种情况：
switch 42.parity {
case .even:
print("Even Number")
case .odd:
print("Odd Number")
}
