Problem: For a positive integer N, the maximum integer of an index that is not more than N and is 2.
INT floor (int N) {
n = n | n >> 1;
N = N | n >> 2;
n = n | n >> 4;
n = n | n >> 8;
n = n | n >> 16;
Return n- (n >> 1);
}
It's really the most efficient program I found, as long as 12 instructions.
In addition, it is generally like this problem.
m = 1;
While (m <= n) m << 1;
RETURN M >> 1;
It looks more concise but the efficiency is low.
