maxProfit.go

package bestTimeToBuyAndSellStockII

//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:
//
//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.

func maxProfit(prices []int) int {
	var (
		buyPrice, profit int
		buyFlag          bool
	)

	for i, v := range prices {
		if !buyFlag && (i+2 <= len(prices)) && prices[i+1] > v {
			buyPrice = v
			buyFlag = true
		}
		if buyFlag && ((i == len(prices)-1) || prices[i+1] < v) {
			profit += v - buyPrice
			buyPrice = 0
			buyFlag = false
		}
	}
	return profit
}