c++ - 复制整数位的最快方法

Question

复制整数位的最快方法是什么。

例如，

17 -> 10001

复制后:1100000011

Answer 1

看起来像是位交错的变体。

Interleave bits the obvious way

(modified from http://graphics.stanford.edu/~seander/bithacks.html)

unsigned int x = 17;
unsigned int z = 0; // z gets the resulting Morton Number.

for (int i = 0; i < sizeof(x) * CHAR_BIT; i++) // unroll for more speed...
{
  z |= (x & 1U << i) << i | (x & 1U << i) << (i + 1);
}

参见 http://graphics.stanford.edu/~seander/bithacks.html#InterleaveTableObvious更多方法。