[LeetCode]Best Time to Buy and Sell Stock III

Best Time to Buy and Sell Stock III

Say you have an array for which the ith element is the price of a given stock on day i.

Design an algorithm to find the maximum profit. You may complete at most two transactions.

Note:
You may not engage in multiple transactions at the same time (ie, you must sell the stock before you buy again).

和Best Time to Buy and Sell Stock很接近，需要维护两个vector使得两次交易一次在区间【0-i】，一次在区间【i，n-1】。

每个区间内的求解最大收益的方法和Best Time to Buy and Sell Stock几乎一样。

取两个区间收益和最大的的结果为最终结果。

class Solution {
public:
    int maxProfit(vector<int>& prices) {
        if (prices.size()<2) return 0;
        int result=0;
        int n = prices.size();
        vector<int> left(n,0);
        vector<int> right(n,0);
        int cur_min = prices[0];
        int cur_result = 0;
        for(int i=1;i<n;i++)
        {
            cur_result = max(cur_result,prices[i]-cur_min);
            left[i] = cur_result;
            cur_min = min(cur_min,prices[i]);
        }
        int cur_max = prices[n-1];
        cur_result = 0;
        for(int i=n-2;i>0;i--)
        {
            cur_result = max(cur_result,cur_max-prices[i]);
            right[i] = cur_result;
            cur_max = max(cur_max,prices[i]);
        }
        for(int i=1;i<n;i++)
        {
            result = max(result,left[i]+right[i]);
        }
        return result;
    }
};