买卖股票的最佳时机

class Solution {  
public:  
    /** 
     * @param prices: Given an integer array 
     * @return: Maximum profit 
     */  
    int maxProfit(vector<int> &prices) {  
        // write your code here  
        int ret = 0;  
        if(prices.size()<2)  
            return ret;  
        int lowest = prices[0];  
        for(int i=1;i<prices.size();i++)  
        {  
            int cur = prices[i];  
            ret = max(ret,cur-lowest);  
            lowest  = min(lowest,cur);  
        }  
        return ret;  
    }  
};