1、最大连续子数组
    https://leetcode-cn.com/problems/lian-xu-zi-shu-zu-de-zui-da-he-lcof/solution/jian-dan-dp-by-1nxctrvewn-itv5/
    dp[i] 代表到i时的最大子序列的值，由dp[i-1] + 当前值 和当前值相比
    （如果当前值大于前子序列+当前值，那么当前值就是最大子序列）

    1. var maxSubArray = function(nums) {
    2.     if (!nums.length) return
    3.     let max_here = nums[0]
    4.     let max_so_far = nums[0]
    5.     for (let i = 1; i < nums.length; i++) {
    6.          max_here = Math.max(nums[i], max_here + nums[i])
    7.          max_so_far = Math.max(max_here, max_so_far)
    8.     }
    9.     return max_so_far
    10. };

    2、股票的最大利润
    https://leetcode-cn.com/problems/gu-piao-de-zui-da-li-run-lcof/solution/

    1. var maxProfit = function(prices) {
    2.     let min = Number.MAX_VALUE
    3.     let max = 0
    4.     for (let p of prices) {
    5.         max = Math.max(p - min, max) 
    6.         min = Math.min(min, p)
    7.     }
    8.     return max
    9. };