Swift -运算符和循环结构

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//: Playground - noun: a place where people can play

import UIKit

var str = "Hello, playground"

//赋值符号

//var a = 3

//控制流 （顺序结构， 循环结构， 选择结构）

//循环结构

//for in

for i in -99...99 {

i*i

}

var result = 1

var base = 2

var power = 10

for _ in 1...power {//_忽略值的使用

result *= base

}

result

//for 循环

for var i = -99 ; i <= 99; i++ {//swift3 报错

i*i

}

//while

var  aWin = 0

var  bWin = 0

var  game = 0

while aWin < 3 && bWin < 3 {

game = game + 1

let a  = arc4random_uniform(6) + 1

let b  = arc4random_uniform(6) + 1

print("a is \(a), b is \(b). ",  terminator: "")

if a > b {

print("A win")

bWin = 0

aWin = aWin + 1

}

else if a < b {

print("B win")

bWin = bWin + 1

aWin = 0

}

else {

print("draw")

aWin = 0

bWin = 0

}

}

print("game is \(game)")

repeat - while 至少要执行一次循环

var aWin = false

var bwin = false

repeat {

let a = arc4random_uniform(6) + 1

let b = arc4random_uniform(6) + 1

print("s is \(a), b is \(b).")

if a > b {

aWin = true

}

else if a < b {

bwin = true

}

else {

print("draw ")

}

print("")

}while !aWin && !bwin

let winner  = aWin ? "A" : "B"

print("\(winner) win !!")

//选择结构

let poin = (0, 0)

switch poin {

case (0, 0):

print("It is Origin")

fallthrough//允许进入下一个判断语法中

case (_, 0):

print("It is on x-axis")

default:

print("It is just an ordinary point")

}

// x^4 - y^2 = 15*x*y 求一组值

findAnswer:

for m in 1...300 {

for n in 1...300 {

if m*m*m - n*n == 15*m*n {

print(m,n)

break findAnswer

}

}

}

//while

let poin = (3,3)

switch poin {

case let (x, y) where x == y:

print("It is On the line x == y")

case let (x, y) where x == -y:

print("It is On the line x == -y")

default:

print("It is a poin")

}

let age = 19

if case 10...19 = age {

print("You are is a teenager !")

}