class Solution {
public:
    /**
     * 
     * @param prices int整型vector 
     * @return int整型
     */
    int maxProfit(vector<int>& prices) {
        // write code here
        int ans = 0, minp = INT_MAX;
        for (int i = 0; i < prices.size(); i++) {
            if (prices[i] >= minp) {
                ans = max(ans, prices[i] - minp);
            }
            minp = min(minp, prices[i]);
        }
        return ans;
    }
};