Merge f40edcf into bb91eec

README.md

@@ -405,4 +405,5 @@ problems from
 * [Day 405](https://github.com/vaskoz/dailycodingproblem-go/issues/819)
 * [Day 406](https://github.com/vaskoz/dailycodingproblem-go/issues/821)
 * [Day 407](https://github.com/vaskoz/dailycodingproblem-go/issues/823)
+* [Day 408](https://github.com/vaskoz/dailycodingproblem-go/issues/825)
 

day408/problem.go

@@ -0,0 +1,29 @@
+package day408
+
+// MaxProfit returns the maximum possible profit given
+// exactly 'k' buy/sell pairs.
+// Runs in O(N*k) time and O(N*k) space.
+func MaxProfit(prices []int, k int) int {
+	profits := make([][]int, k+1)
+	for i := range profits {
+		profits[i] = make([]int, len(prices)+1)
+	}
+
+	for i := 1; i <= k; i++ {
+		diff := -int(^uint(0)>>1) - 1
+		for j := 1; j < len(prices); j++ {
+			diff = max(diff, profits[i-1][j-1]-prices[j-1])
+			profits[i][j] = max(profits[i][j-1], prices[j]+diff)
+		}
+	}
+
+	return profits[k][len(prices)-1]
+}
+
+func max(a, b int) int {
+	if a > b {
+		return a
+	}
+
+	return b
+}

day408/problem_test.go

@@ -0,0 +1,31 @@
+package day408
+
+import "testing"
+
+// nolint
+var testcases = []struct {
+	prices    []int
+	k         int
+	maxProfit int
+}{
+	{[]int{5, 2, 4, 0, 1}, 2, 3},
+	{[]int{12, 14, 17, 10, 14, 13, 12, 15}, 3, 12},
+}
+
+func TestMaxProfit(t *testing.T) {
+	t.Parallel()
+
+	for _, tc := range testcases {
+		if maxProfit := MaxProfit(tc.prices, tc.k); maxProfit != tc.maxProfit {
+			t.Errorf("Expected %v got %v", tc.maxProfit, maxProfit)
+		}
+	}
+}
+
+func BenchmarkMaxProfit(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for _, tc := range testcases {
+			MaxProfit(tc.prices, tc.k)
+		}
+	}
+}