【leetcode】121-Best Time to Buy and Sell Stock

class Solution {
public:
    int maxProfit(vector<int>& prices) {
        int res = 0;
        for(int i=0; i<prices.size(); i++)
        {
            int buy_price = prices[i];
            for(int j=i+1; j<prices.size(); j++)
            {
                int sell_price = prices[j];
                int tmp = sell_price - buy_price;
                if(tmp>res) res = tmp;
            }         
        }
        return res;
        
    }
};

class Solution {
public:
    int maxProfit(vector<int>& prices) {
        int min_price = INT_MAX;
        int max_profit = 0;
        for(int i=0; i<prices.size(); i++)
        {
            if(min_price> prices[i]) min_price = prices[i];
            else if(prices[i]-min_price>max_profit) max_profit = prices[i]-min_price;
        }
        return max_profit;
    }
};