profit.go

// Solution to the interview question of finding ideal purchase/sale times and profits for
// a history of a single stock, in Go

package main

import "fmt"

// Finds the maximum profit to be had from buying and selling at a given price
func MaxProfit(prices []int) (buy int, sell int, profit int) {
	profit = 0
	buy = 0
	sell = 0
	currbuy := 0
	for i, _ := range prices {
		if i == 0 {
			continue // skip first index
		}
		buyPrice := prices[currbuy]
		currPrice := prices[i]
		if currPrice < buyPrice {
			currbuy = i
		} else {
			// On new better profit, update the tracker for when we buy, sell and the profit
			potentialProfit := currPrice - buyPrice
			if potentialProfit > profit {
				profit = potentialProfit
				buy = currbuy
				sell = i
			}
		}
	}

	return
}

func main() {
	prices := []int{5, 6, 7, 3, 5, 9, 0, 10, -1, 12}
	buy, sell, profit := MaxProfit(prices)
	fmt.Printf("buy %v, sell %v, profit %v\n", buy, sell, profit) // => 7
}