Merge pull request #602 from vaskoz/day295

Day295

README.md

@@ -301,3 +301,4 @@ problems from
 * [Day 288](https://github.com/vaskoz/dailycodingproblem-go/issues/590)
 * [Day 290](https://github.com/vaskoz/dailycodingproblem-go/issues/594)
 * [Day 291](https://github.com/vaskoz/dailycodingproblem-go/issues/596)
+* [Day 295](https://github.com/vaskoz/dailycodingproblem-go/issues/601)

day295/problem.go

@@ -0,0 +1,23 @@
+package day295
+
+// PascalTriangleRow returns a particular row in Pascal's triangle.
+// Runs in O(row) time and space.
+func PascalTriangleRow(row int) []int {
+	result := make([]int, row+1)
+	for entry := range result {
+		result[entry] = combinations(row, entry)
+	}
+	return result
+}
+
+func combinations(n, k int) int {
+	return factorial(n) / (factorial(k) * factorial(n-k))
+}
+
+func factorial(n int) int {
+	result := 1
+	for i := 2; i <= n; i++ {
+		result *= i
+	}
+	return result
+}

day295/problem_test.go

@@ -0,0 +1,38 @@
+package day295
+
+import (
+	"reflect"
+	"testing"
+)
+
+// nolint
+var testcases = []struct {
+	row      int
+	expected []int
+}{
+	{0, []int{1}},
+	{1, []int{1, 1}},
+	{2, []int{1, 2, 1}},
+	{3, []int{1, 3, 3, 1}},
+	{4, []int{1, 4, 6, 4, 1}},
+	{5, []int{1, 5, 10, 10, 5, 1}},
+	{6, []int{1, 6, 15, 20, 15, 6, 1}},
+	{7, []int{1, 7, 21, 35, 35, 21, 7, 1}},
+}
+
+func TestPascalTriangleRow(t *testing.T) {
+	t.Parallel()
+	for _, tc := range testcases {
+		if result := PascalTriangleRow(tc.row); !reflect.DeepEqual(result, tc.expected) {
+			t.Errorf("Expected %v, got %v", tc.expected, result)
+		}
+	}
+}
+
+func BenchmarkPascalTriangleRow(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for _, tc := range testcases {
+			PascalTriangleRow(tc.row)
+		}
+	}
+}