Merge 0a516b6 into 42784b0

README.md

@@ -235,3 +235,4 @@ problems from
 * [Day 222](https://github.com/vaskoz/dailycodingproblem-go/issues/458)
 * [Day 223](https://github.com/vaskoz/dailycodingproblem-go/issues/460)
 * [Day 224](https://github.com/vaskoz/dailycodingproblem-go/issues/462)
+* [Day 225](https://github.com/vaskoz/dailycodingproblem-go/issues/465)

day225/problem.go

@@ -0,0 +1,24 @@
+package day225
+
+import "math/bits"
+
+// JosephusGeneral is the general case solution.
+func JosephusGeneral(n, k int) int {
+	if k == 2 {
+		return josephusGeneralK2(n)
+	}
+	return josephusGeneral(n, k) + 1
+}
+
+func josephusGeneralK2(n int) int {
+	highestBit := bits.Len64(uint64(n))
+	highestBit = 1 << uint(highestBit-1)
+	return 2*(n-highestBit) + 1
+}
+
+func josephusGeneral(n, k int) int {
+	if n == 1 {
+		return 0
+	}
+	return (josephusGeneral(n-1, k) + k) % n
+}

day225/problem_test.go

@@ -0,0 +1,28 @@
+package day225
+
+import "testing"
+
+var testcases = []struct {
+	n, k, survivor int
+}{
+	{5, 2, 3},
+	{41, 2, 19},
+	{5, 3, 4},
+}
+
+func TestJosephusGeneral(t *testing.T) {
+	t.Parallel()
+	for _, tc := range testcases {
+		if survivor := JosephusGeneral(tc.n, tc.k); survivor != tc.survivor {
+			t.Errorf("Given N=%d, k=%d, expected %d, got %d", tc.n, tc.k, tc.survivor, survivor)
+		}
+	}
+}
+
+func BenchmarkJosephusGeneral(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for _, tc := range testcases {
+			JosephusGeneral(tc.n, tc.k)
+		}
+	}
+}