let numbers = [1, 2, 3, 4, 5]
var random = numbers.shuffled()
while random == numbers {
random = numbers.shuffled()
}
repeat 洗牌
let numbers = [1, 2, 3, 4, 5]
var random: [Int]
repeat {
random = numbers.shuffled()
} while random == numbers
4.4 退出循环
break 关键字为退出循环标识,不再执行循环体
var countDown = 10
while countDown >= 0 {
print(countDown)
if countDown == 4 {
print("I'm bored. Let's go now!")
break
}
countDown -= 1
}
let scores = [1, 8, 4, 3, 0, 5, 2]
var count = 0
for score in scores {
if score == 0 {
break
}
count += 1
}
4.5 退出多层循环
退出多层循环的意义在于优化性能
Step 1 给外层循环加标签
Step 2 在内层循环 需要退出的位置执行 break + 外层循环标签
outerLoop: for i in 1...10 {
for j in 1...10 {
let product = i * j
print ("\(i) * \(j) is \(product)")
if product == 50 {
print("It's a bullseye!")
break outerLoop
}
}
}
4.6 跳过循环
continue 关键字跳过当前行,不跳出循环体,继续执行下一次循环
for i in 1...10 {
if i % 2 == 1 {
continue
}
print(i)
}