我正在寻找计算unsigned int中位转换次数的最快方法.
如果int包含：0b00000000000000000000000000001010
转换次数为：4
如果int包含：0b00000000000000000000000000001001
转换次数为：3
语言是C.
解决方法
int numTransitions(int a)
{
int b = a >> 1; // sign-extending shift properly counts bits at the ends
int c = a ^ b; // xor marks bits that are not the same as their neighbors on the left
return CountBits(c); // count number of set bits in c
}
为了有效实施CountBits,请参见http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel
