[英]How to get the position of the first set bit of a number
for example, my definition looks like the following: 例如,我的定义如下所示:
#define AA 0x0000000000000001LL
#define BB 0x0000000000000002LL
#define CC 0x0000000000000004LL
#define DD 0x0000000000000008LL
#define EE 0x0000000000000010LL
#define FF 0x0000000000000020LL
#define GG 0x0000000000000040LL
#define HH 0x0000000000000080LL
I would like to get the position of the first set bit (counting backwards from the least significant bit) from the maximum definition. 我想从最大定义中获取第一个设置位(从最低有效位开始倒数)的位置。
h = getAmountFromBitwise(HH);
output of h is 8;
b = getAmountFromBitwise(BB);
output b is 2;
Is there any better way to implement getAmountFromBitwise()? 有没有更好的方法来实现getAmountFromBitwise()?
int getAmountFromBitwise(long long input) {
2^x = input;
y=x+1;
return y;
}
I would use this as your getAmountFromBitwise()
. 我将其用作您的
getAmountFromBitwise()
。
int highest_bit_set(long long n) {
int result = 1;
while(n >>= 1) /* keep shifting right until n == 0 */
result++;
return result;
}
Note that this requires that n != 0
for a correct result. 注意,这要求
n != 0
以获得正确的结果。
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