[Swift]LeetCode152. 乘积最大子序列 | Maximum Product Subarray

概述Given an integer array nums, find the contiguous subarray within an array (containing at least one number) which has the largest product. Example 1: Input: [2,3,-2,4]Output: Explanation: [2,3] has

Given an integer array nums,find the contiguous subarray within an array (containing at least one number) which has the largest product.

Example 1:

input: [2,3,-2,4]Output: Explanation: [2,3] has the largest product 6.6

Example 2:

input: [-2,-1]Output: 0Explanation: The result cannot be 2,because [-2,-1] is not a subarray.

给定一个整数数组 nums ，找出一个序列中乘积最大的连续子序列（该序列至少包含一个数）。

示例 1:

输入: [2,4]输出: 解释: 子数组 [2,3] 有最大乘积 6。6

示例 2:

输入: [-2,-1]输出: 0解释: 结果不能为 2,因为 [-2,-1] 不是子数组。

12ms

 1 class Solution { 2     func maxProduct(_ nums: [Int]) -> Int { 3         guard nums.count > 0 else { return 0 } 4          5         var minValue = nums[0],maxValue = nums[0],finalValue = nums[0] 6          7         for i in 1..<nums.count { 8             if nums[i] > 0 { 9                 maxValue = max(nums[i],maxValue * nums[i])10                 minValue = min(nums[i],minValue * nums[i])11             }else {12                 var tmp = maxValue13                 maxValue = max(nums[i],minValue * nums[i])14                 minValue = min(nums[i],tmp * nums[i])15             }16             finalValue = max(finalValue,maxValue)17         }18         19         return finalValue20     }21 }

16ms

 1 class Solution { 2     func maxProduct(_ nums: [Int]) -> Int { 3         return getResult(nums) 4     } 5      6    private func getResult(_ array: [Int]) -> Int { 7         var result = array[0] 8         var prevIoUsMin = array[0] 9         var prevIoUsMax = array[0]10         var currentMin = array[0]11         var currentMax = array[0]12 13         for el in array.dropFirst() {14             currentMax = max(max(prevIoUsMax * el,prevIoUsMin * el),el)15             currentMin = min(min(prevIoUsMax * el,el)16             result = max(currentMax,result)17             prevIoUsMax = currentMax18             prevIoUsMin = currentMin19         }20 21         return result22     }23 }

28ms

 1 class Solution { 2     func maxProduct(_ nums: [Int]) -> Int { 3         guard !nums.isEmpty else { return 0 } 4  5         var ret = nums.first! 6         var (iMin,iMax) = (nums.first!,nums.first!) 7  8         for n in nums.dropFirst() { 9             if n < 0 {10                 (iMin,iMax) = (iMax,iMin)11             }12 13             iMin = min(n,iMin * n)14             iMax = max(n,iMax * n)15 16             ret = max(ret,iMax)17         }18 19         return ret20     }21 }

32ms

 1 class Solution { 2  3     func maxProduct(_ nums: [Int]) -> Int { 4         guard nums.count > 0 else { 5             return 0 6         } 7          8         var minimum = 1 9         var maximum = 110         var oldMax = maximum11         var globalMax = nums[0]12         13         for num in nums {14             if num < 0 {15                 oldMax = maximum16                 maximum = max(num,minimum*num)17                 minimum = min(num,oldMax*num)18             } else {19                 maximum = max(num,maximum*num)20                 minimum = min(num,minimum*num)21             }22             globalMax = max(globalMax,maximum)23         }24         25         return globalMax26     }27 }

36ms

 1 class Solution { 2     func maxProduct(_ nums: [Int]) -> Int { 3         var lhs = 1 4         var rhs = 1 5         var maxhs = nums[0] 6          7         for i in 0..<nums.count { 8             lhs *= nums[i] 9             rhs *= nums[nums.count - i - 1]10             maxhs = max(maxhs,lhs,rhs)11             12             if lhs == 0 { lhs = 1}13             if rhs == 0 { rhs = 1}14             15         }16         return maxhs17     }18 }

40ms

 1 class Solution { 2     func maxProduct(_ nums: [Int]) -> Int { 3         guard nums.count > 0 else { 4             return 0 5         } 6  7         var maxN = nums[0],maxT = 1,minT = 1 8         for i in 0..<nums.count { 9             let tmp1 = maxT * nums[i]10             let tmp2 = minT * nums[i]11             maxN = max(maxN,tmp1,tmp2)12             maxT = max(tmp1,tmp2,1)13             minT = min(tmp1,1)14         }15         return maxN16     }17 }

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