[152] 乘积最大子数组

/*
 * @lc app=leetcode.cn id=152 lang=javascript
 *
 * [152] 乘积最大子数组
 */

// @lc code=start
/**
 * @param {number[]} nums
 * @return {number}
 */
var maxProduct = function (nums) {
  const maxProductMemo = []
  const minProductMemo = []
  maxProductMemo[0] = nums[0]
  minProductMemo[0] = nums[0]
  let max = nums[0]
  for (let i = 1; i < nums.length; i++) {
    // 数组里面存在负数，相乘变为正就是最大，所以比较三者之间的最大值和最小值
    maxProductMemo[i] = Math.max(
      nums[i],
      nums[i] * maxProductMemo[i - 1],
      nums[i] * minProductMemo[i - 1]
    )
    // console.log('object', maxProductMemo[i-1])
    minProductMemo[i] = Math.min(
      nums[i],
      nums[i] * maxProductMemo[i - 1],
      nums[i] * minProductMemo[i - 1]
    )
    max = Math.max(max, maxProductMemo[i])
  }
  return max
}
// @lc code=end