best-time-to-buy-and-sell-stock

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