LeetCode122. Best Time to Buy and Sell Stock II

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 as many transactions as you like (i.e., buy one and sell one share of the stock multiple times).

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

Example 1:

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Input: [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.

Example 2:

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Input: [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.
Note that you cannot buy on day 1, buy on day 2 and sell them later, as you are
engaging multiple transactions at the same time. You must sell before buying again.

Example 3:

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Input: [7,6,4,3,1]
Output: 0
Explanation: In this case, no transaction is done, i.e. max profit = 0.

贪心+动态规划

122

从头开始遍历,相当于是一串串的利润总和,而且这些利润片段要最大,所以用到贪心算法,只要后面的数比前面的大,就将他们的差值加入到ret总和里面。

my code in cpp

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int maxProfit(vector<int>& prices) {
if(prices.empty()) return 0;
int ret=0;
for(int i=0;i<prices.size()-1;i++)
if(prices[i+1]>prices[i]) ret+=prices[i+1]-prices[i];
return ret;
}
Thanks for Support.