maximum-product-subarray.js

/**
 * Maximum Product Subarray
 *
 * 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: 6
 * Explanation: [2,3] has the largest product 6.
 *
 * Example 2:
 *
 * Input: [-2,0,-1]
 * Output: 0
 * Explanation: The result cannot be 2, because [-2,-1] is not a subarray.
 */

/**
 * @param {number[]} nums
 * @return {number}
 */
const maxProduct = nums => {
  let res = nums[0];
  let min = nums[0];
  let max = nums[0];

  for (let i = 1; i < nums.length; i++) {
    if (nums[i] > 0) {
      max = Math.max(nums[i], max * nums[i]);
      min = Math.min(nums[i], min * nums[i]);
    } else {
      const tmp = max;
      max = Math.max(nums[i], min * nums[i]);
      min = Math.min(nums[i], tmp * nums[i]);
    }

    res = Math.max(res, max);
  }

  return res;
};

export { maxProduct };