CF768B

Author: EndlessCheng

main/700-799/768B.go

@@ -0,0 +1,31 @@
+package main
+
+import (
+	. "fmt"
+	"io"
+	"math/bits"
+)
+
+// github.com/EndlessCheng/codeforces-go
+func CF768B(in io.Reader, out io.Writer) {
+	var n, l, r uint64
+	Fscan(in, &n, &l, &r)
+	tot := (uint64(1)<<bits.Len64(n) - 1) >> 1
+	f := func(m uint64) (res uint64) {
+		for n, tot := n, tot; m > 0; n >>= 1 {
+			if m >= tot {
+				m -= tot
+				res += n / 2
+				if m > 0 {
+					m--
+					res += n & 1
+				}
+			}
+			tot >>= 1
+		}
+		return
+	}
+	Fprint(out, f(r)-f(l-1))
+}
+
+//func main() { CF768B(os.Stdin, os.Stdout) }

main/700-799/768B_test.go

@@ -0,0 +1,22 @@
+package main
+
+import (
+	"github.com/EndlessCheng/codeforces-go/main/testutil"
+	"testing"
+)
+
+// https://codeforces.com/problemset/problem/768/B
+// https://codeforces.com/problemset/status/768/problem/B
+func TestCF768B(t *testing.T) {
+	// just copy from website
+	rawText := `
+inputCopy
+7 2 5
+outputCopy
+4
+inputCopy
+10 3 10
+outputCopy
+5`
+	testutil.AssertEqualCase(t, rawText, 0, CF768B)
+}