leetcode-121-best time to buy and sell stock

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

还有一种方法是从尾部开始搜索，大的就标记为售出价。