LeetCode 122. Best Time to Buy and Sell Stock II

Problem

Say you have an array prices 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:

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:

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:

Input: [7,6,4,3,1]

Output: 0

Explanation: In this case, no transaction is done, i.e. max profit = 0.

 

-Summary- 

Solving with greedy algorithm

1. For each element in the array, compare the first element and the second element.

2. If the first element is smaller than the second element, you add the profit. (Repeat this until you compare all elements in the array).

3. Once all loop is done, you will have the maximum profit.

 

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