Easy-34

leetcode       122. Best Time to Buy and Sell Stock II          

Say you have an array for which the i^th element is the price of a given stock on dayi.

Design an algorithm to find the maximum profit. You may complete as many transactions as you like (ie, buy one and sell one share of the stock multiple times). However, you may not engage in multiple transactions at the same time (ie, you must sell the stock before you buy again).

AC:

int maxProfit(int* prices, int pricesSize) {
    int start=-1,end=-1,result=0;
    if(pricesSize<=1)
    {
        return 0;
    }
    for(int i=0;i<pricesSize-1;i++)
    {
        if(prices[i+1]>=prices[i]&&start<0)
        {
            start=i;
        }
        if(start>=0&&prices[i+1]>=prices[i])
        {
            end=i+1;
        }
       
        if((start>=0&&end>=0&&prices[i+1]<prices[i])||(start>=0&&end==pricesSize-1))
        {
            result+=prices[end]-prices[start];
            i=end;
            start=-1;end=-1;
        }
    }
   
    return result;
}

tips：抱着不过的心，居然过了。。。单次循环，设置买入点和卖出点，然后计算利润的条件。找到第一个后一天大于今天的价格，设置为买入，  当后一天的价格大于前一天则继续持有股票，否则卖出。并设置买入点从卖出点的后一天开始。 一直持有股票，当卖出点为天数的最大值时，也卖出。