popcount

README.md

@@ -16,3 +16,4 @@
 |12|gcd|最大公约数|
 |13|type|类型别名|
 |14|tempconv&kelvins|开尔文温度转换|
+|15|popcount&test|置位数量|

popcount/popcount.go

@@ -0,0 +1,19 @@
+package popcount
+
+var pc [256]byte
+
+func init() {
+	for i := range pc {
+		pc[i] = pc[i/2] + byte(1&i)
+	}
+}
+func PopCount(x uint64) int {
+	return int(pc[byte(x>>(0*8))] +
+		pc[byte(x>>(1*8))] +
+		pc[byte(x>>(2*8))] +
+		pc[byte(x>>(3*8))] +
+		pc[byte(x>>(4*8))] +
+		pc[byte(x>>(5*8))] +
+		pc[byte(x>>(6*8))] +
+		pc[byte(x>>(7*8))])
+}

test/test.go

@@ -0,0 +1,11 @@
+package main
+
+import (
+	"fmt"
+	"popcount"
+)
+
+func main() {
+	res := popcount.PopCount(7976543532654546)
+	fmt.Println(res)
+}