LeetCode Blind 75 in Swift: Solving the "Maximum Product Subarray" Problem

Problem: Maximum Product Subarray

The Maximum Product Subarray problem asks you to find the contiguous subarray within an array (containing at least one number) that has the largest product.

Example:

Input: nums = [2, 3, -2, 4]
Output: 6
Explanation: [2, 3] has the largest product = 6.

Swift Solution

class Solution {
    func maxProduct(_ nums: [Int]) -> Int {
        var currentMax = nums[0]
        var currentMin = nums[0]
        var result = nums[0]

        for num in nums.dropFirst() {
            let tempMax = currentMax
            currentMax = max(num, currentMax * num, currentMin * num)
            currentMin = min(num, tempMax * num, currentMin * num)
            result = max(result, currentMax)
        }
        
        return result
    }
}

let solution = Solution()
let nums = [2, 3, -2, 4]
let result = solution.maxProduct(nums)
print(result) // Output: 6

Explanation

In this solution, we maintain two values: the maximum product and the minimum product at each point in the array. This is because a negative number can turn a minimum product into a maximum when multiplied. As we traverse the array, we calculate the maximum and minimum products at each step and update the result accordingly.

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