Question

如何使用闭包计算最大连续正数？

var numbers = [1,3,4,-1,-2,5,2,-2,-3,-4,5]
//in this case it should be 3

print(numbers.reduce(0, { $1 > 0 ? $0 + 1 : $0 } ))//this counts total positive numbers

Answer 1

更新：更简单的解决方案：将数组拆分为正元素，并确定最大切片长度：

let  numbers = [1,3,4,-1,-2,5,2,-2,-3,-4,5]
let maxConsecutive = numbers.split(whereSeparator: { $0 <= 0 }).map { $0.count }.max()!
print(maxConsecutive) // 3

旧答案：）使用Swift running sum中的想法：

let  numbers = [1,3,4,-1,-2,5,2,-2,-3,-4,5]

let maxConsecutive = numbers.map({
    () -> (Int) -> Int in var c = 0; return { c = $0 > 0 ? c + 1 : 0; return c }
}()).max()!

这里map()将每个数组元素映射到连续正数的计数数字到元素位置，在这种情况下

[1, 2, 3, 0, 0, 1, 2, 0, 0, 0, 1]

转换创建为“立即评估闭包“捕获保存当前数量的变量c 连续的正数。转换增加或重置c，并返回更新后的值。

如果数组可能很大，则将其更改为

let maxConsecutive = numbers.lazy.map( ... ).max()!

以确定最大游程长度而不创建中间阵列。

Answer 2

var currentResult = 0
var maxResult = 0
for i in numbers {
    currentResult = i > 0 ? currentResult + 1 : 0
    if maxResult < currentResult {
       maxResult = currentResult
    }
}
print(maxResult)

没有闭包的解决方案

Answer 3

var numbers = [1, 3, 4, -1, -2, 5, 2, -2, -3, -4, 5]

let result = numbers.reduce((current: 0, max: 0)) { result, number in
    var value = result

    if number > 0 {
        value.current += 1
        value.max = max(value.current, value.max)
    } else {
        value.current = 0
    }

    return value
}



result.max

Answer 4

生成子序列：

let numbers = [1,3,4,-1,-2,5,2,-2,-3,-4,5]
let subsequences: [[Int]] = numbers.reduce(into: []) { (result, number) in
    guard
        var currentSequence = result.last,
        let lastNumber = currentSequence.last
    else {
        result = [[number]]
        return
    }

    if number == lastNumber + 1 {
        currentSequence.append(number)
        result.removeLast()
        result.append(currentSequence)
    } else {
        result.append([number])
    }
}
let longest = subsequences.max { $0.count < $1.count }
print(subsequences)
print("Longest subsequence: \(longest)")
print("Longest length: \(longest?.count)")

Answer 5

检测数组中连续的三个数

var  data = [1,2,5,4,56,6,7,9,6,5,4,5,1,2,5,4,56,6,7,9,8,1,1,2,5,4,56,6,7,9,8,1,1,2,5,4,56,6,7,9,8,1,1,2,5,4,56,6,7,9,8,1,1,2,5,4,56,6,7,9,8,11,2,5,4,56,6,7,9,8,1,2,3]

for i in 0...data.count{
    if i+2 < data.count{
        if Int(data[i] + data[i+2]) / 2 == data[i+1] && Int(data[i] + data[i+2]) % data[i+1] == 0 && data[i+1] != 1 && data[i] < data[i+1]{
            print(data[i] ,data[i+1], data[i+2])
        }
    }
}

快速最大连续正数

5 个答案: