LeetCode Best Time to Buy and Sell Stock

原题链接在这里：https://leetcode.com/problems/best-time-to-buy-and-sell-stock/

与Maximum Subarray相似，都是全局最优与局部最优问题。

维护一个局部最优解，和一个全局最优解, 先更新局部最优解, 要么是原来的局部最优加上i天与i-1天得差价，要么是0(i天股价没有i-1天高), 然后维护全局最优，最后返回全局最优。

AC Java:

public class Solution {
    public int maxProfit(int[] prices) {
        //采用局部最优和全局最优
        if(prices == null || prices.length <= 1){
            return 0;
        }
        int local = 0;
        int global = 0;
        for(int i = 1; i<prices.length; i++){
            local = Math.max(local+prices[i]-prices[i-1],0);
            global = Math.max(local,global);
        }
        return global;
    }
}

后面有多个进阶版本。

Best Time to Buy and Sell Stock II

Best Time to Buy and Sell Stock III

Best Time to Buy and Sell Stock IV