add new solutions

solutions/7/q714/solution.go

@@ -0,0 +1,33 @@
+package q714
+
+// Note: could be done faster with dynamic programming
+
+func maxProfit(prices []int, fee int) int {
+	var low, high, profit int
+	bought := false
+	for i := range prices {
+		if bought {
+			high = max(high, prices[i])
+			if high-prices[i] > fee { // should have sold earlier or not bought
+				if high-low > fee {
+					profit += high - low - fee
+				}
+				bought = false
+			} else if prices[i] < low { // regret buying too early
+				low, high = prices[i], prices[i]
+			}
+		}
+
+		if !bought && i < len(prices)-1 && prices[i+1] > prices[i] {
+			bought = true // buy the dip
+			low, high = prices[i], prices[i]
+		}
+	}
+
+	if bought && high-low > fee {
+		profit += high - low - fee
+	}
+	return profit
+}
+
+var _ = maxProfit