[leetcode 121] Best Time to Buy and Sell Stock

Say you have an array for which the ith element is the price of a given stock on day i.

If you were only permitted to complete at most one transaction (ie, buy one and sell one share of the stock), design an algorithm to find the maximum profit.

思路：动态规划。记录最小的price， 转移方程res = max(res, prices[i]-min_price)

class Solution {public:    int maxProfit(vector<int> &prices) {        int res = 0;        if (prices.size() < 2) {            return res;        }        int min_price = prices[0];        for (auto i = 1; i < prices.size(); i++) {            res = max(res, prices[i]-min_price);            min_price = min(min_price, prices[i]);        }        return res;    }};