题目名称

122. Best Time to Buy and Sell Stock II

题目描述

You are given an integer array prices where prices[i] is the price of a given stock on the ith day.

On each day, you may decide to buy and/or sell the stock. You can only hold at most one share of the stock at any time. However, you can buy it then immediately sell it on the same day.

Find and return the maximum profit you can achieve.

Example 1:

Input: prices = [7,1,5,3,6,4]
Output: 7
Explanation: Buy on day 2 (price = 1) and sell on day 3 (price = 5), profit = 5-1 = 4.
Then buy on day 4 (price = 3) and sell on day 5 (price = 6), profit = 6-3 = 3.
Total profit is 4 + 3 = 7.
Example 2:

Input: prices = [1,2,3,4,5]
Output: 4
Explanation: Buy on day 1 (price = 1) and sell on day 5 (price = 5), profit = 5-1 = 4.
Total profit is 4.
Example 3:

Input: prices = [7,6,4,3,1]
Output: 0
Explanation: There is no way to make a positive profit, so we never buy the stock to achieve the maximum profit of 0.

Constraints:

1 <= prices.length <= 3 * 104
0 <= prices[i] <= 104

初试思路

这个题之前做过的，但是忘记了。链接：
leetcode(c++)-买卖股票的最佳时机 II
1、动态规划；
2、贪心算法求上升区间高度和。

初试代码

// 我的代码1
class Solution {
public:int maxProfit(vector& prices) {int dp0 = 0;int dp1 = -prices[0];int tmp;for (int i=1; i& prices) {int sum = 0;for(int i = 0; i+1 < size(prices); i++){if (prices[i+1] > prices[i])sum += prices[i+1] - prices[i];}return sum;}
};