best-time-to-buy-and-sell-stock: use greedy algorithm

best-time-to-buy-and-sell-stock/invidam.go

@@ -1,12 +1,10 @@
 func maxProfit(prices []int) int {
-	maxPriceFrom := make([]int, len(prices)+1)
-	for i := len(prices) - 1; i >= 0; i-- {
-		maxPriceFrom[i] = max(maxPriceFrom[i+1], prices[i])
-	}
+	purchasePrice := prices[0]
+	maxBenefit := 0
 
-	maxPriceDiff := 0
-	for i, price := range prices {
-		maxPriceDiff = max(maxPriceDiff, maxPriceFrom[i+1]-price)
+	for _, price := range prices {
+		purchasePrice = min(purchasePrice, price)
+		maxBenefit = max(maxBenefit, price-purchasePrice)
 	}
-	return maxPriceDiff
+	return maxBenefit
 }