maximumProductSubarray.js

/*
Given an integer array nums, find a subarray that has the largest product, and return the product.
The test cases are generated so that the answer will fit in a 32-bit integer.

Example 1:
Input: nums = [2,3,-2,4]
Output: 6
Explanation: [2,3] has the largest product 6.

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

Constraints:
    1 <= nums.length <= 2 * 10^4
    -10 <= nums[i] <= 10
    The product of any prefix or suffix of nums is guaranteed to fit in a 32-bit integer.
*/

/**
 * @param {number[]} nums
 * @return {number}
 */
function maxProduct(nums) {
    let maxSoFar = nums[0];
    let maxEndingHere = nums[0];
    let minEndingHere = nums[0];

    for (let i = 1; i < nums.length; i++) {
        const temp = maxEndingHere;
        maxEndingHere = Math.max(nums[i], maxEndingHere * nums[i], minEndingHere * nums[i]);
        minEndingHere = Math.min(nums[i], temp * nums[i], minEndingHere * nums[i]);
        maxSoFar = Math.max(maxSoFar, maxEndingHere);
    }
    return maxSoFar;
}

// Example usage:
const nums = [2, 3, -2, 4];
console.log(maxProduct(nums)); // Output: 6