121. The best time to buy and sell stocks

Given an array prices , It's the first i Elements prices[i] Represents the number of shares in a given stock i Sky price .

You can only choose One day Buy this stock , And choose A different day in the future Sell the stock . Design an algorithm to calculate the maximum profit you can get .

Return the maximum profit you can make from the deal . If you can't make any profit , return 0 .

Example 1：

 Input ：[7,1,5,3,6,4]
 Output ：5

explain ： In the 2 God （ Stock price = 1） Buy when , In the 5 God （ Stock price = 6） Sell when , Maximum profit = 6-1 = 5 .
Note that profit cannot be 7-1 = 6, Because the selling price needs to be higher than the buying price ; meanwhile , You can't sell stocks before you buy them .

Example 2：

 Input ：prices = [7,6,4,3,1]
 Output ：0

explain ： under these circumstances , No deal is done , So the biggest profit is 0.

Tips ：

1 <= prices.length <= 105
0 <= prices[i] <= 104

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