Merge pull request #880 from vaskoz/day433

Day433

README.md

@@ -427,6 +427,7 @@ problems from
 * [Day 427](https://github.com/vaskoz/dailycodingproblem-go/issues/861)
 * [Day 428](https://github.com/vaskoz/dailycodingproblem-go/issues/864)
 * [Day 429](https://github.com/vaskoz/dailycodingproblem-go/issues/866)
+* [Day 433](https://github.com/vaskoz/dailycodingproblem-go/issues/879)
 * [Day 434](https://github.com/vaskoz/dailycodingproblem-go/issues/870)
 * [Day 435](https://github.com/vaskoz/dailycodingproblem-go/issues/868)
 * [Day 436](https://github.com/vaskoz/dailycodingproblem-go/issues/877)

day433/problem.go

@@ -0,0 +1,18 @@
+package day433
+
+// NextIntSameSetBits returns the next greater
+// integer with the same set bits.
+func NextIntSameSetBits(n int) int {
+	res := 0
+
+	if n != 0 {
+		rightMostBitInt := n & -n
+		nextHigherSetBitInt := n + rightMostBitInt
+		d := n ^ nextHigherSetBitInt
+		d /= rightMostBitInt
+		d >>= 2
+		res = nextHigherSetBitInt | d
+	}
+
+	return res
+}

day433/problem_test.go

@@ -0,0 +1,29 @@
+package day433
+
+import "testing"
+
+// nolint
+var testcases = []struct {
+	n, next int
+}{
+	{6, 9},
+	{156, 163},
+}
+
+func TestNextIntSameSetBits(t *testing.T) {
+	t.Parallel()
+
+	for _, tc := range testcases {
+		if next := NextIntSameSetBits(tc.n); next != tc.next {
+			t.Errorf("Expected %v, got %v", tc.next, next)
+		}
+	}
+}
+
+func BenchmarkNextIntSameSetBits(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for _, tc := range testcases {
+			NextIntSameSetBits(tc.n)
+		}
+	}
+}