121. Best Time to Buy and Sell Stock LeetCode

题意：给出每天股票的价格，只能进行一次交易，求最大收益。
题解：DP，minprice表示1…到i天价格最低的股票，maxprice表示1…i天最大收益。maxprice = max(maxprice,price[i] - minprice).

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