121. Best Time to Buy and Sell Stock

解法

貪心法，紀錄先前最小值，在跟每天的價格比對就好。

程式碼

class Solution {
public:
    int maxProfit(vector<int>& prices) {
        int ans = 0;
        int minn = 10020;

        for(int i = 0; i < prices.size(); i++){
            minn = min(prices[i], minn);
            ans = max(ans, prices[i] - minn);
        }
        return ans;
    }
};