今天底点过了吧？ around 13:10pm - 未名空间MITBBS历史存档

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今天底点过了吧？ around 13:10pm

今天底点过了吧？ around 13:10pm# Stock

m*r2010-04-30 07:04

1 楼

public int isPowerOfTwo(int x)
{
return(
x == 1 || x == 2 || x == 4 || x == 8 || x == 16 || x == 32 ||
x == 64 || x == 128 || x == 256 || x == 512 || x == 1024 ||
x == 2048 || x == 4096 || x == 8192 || x == 16384 ||
x == 32768 || x == 65536 || x == 131072 || x == 262144 ||
x == 524288 || x == 1048576 || x == 2097152 ||
x == 4194304 || x == 8388608 || x == 16777216 ||
x == 33554432 || x == 67108864 || x == 134217728 ||
x == 268435456 || x == 536870912 || x == 1073741824 ||
x == 2147483648);
);
}
这种算O(1)吧，算是最快了吗？

A*k2010-04-30 07:04

2 楼

anyone can confirm?
load 3x etf near 13:10pm

r*l2010-04-30 07:04

3 楼

你这么算的话，几乎所有问题都可以算是O(1)的了。因为精度有限制，即使O(2^n)这种
指数级的复杂度，其实也不会超过2^2147483647这个常数（假设n是32位整数）。

p*i2010-04-30 07:04

4 楼

股神啊

j*32010-04-30 07:04

5 楼

这个看起来有点。。。。有点恶心

A*k2010-04-30 07:04

6 楼

load some SPY and some UPRO
BOT 200 SPY Stock 119.450 USD ISLAND 10:08:45 1.
00
BOT 100 SPY Stock 119.4499 USD SMART 10:10:59 1.
00

【在 A******k 的大作中提到】

: anyone can confirm?
: load 3x etf near 13:10pm

m*r2010-04-30 07:04

7 楼

谢谢上面的回复
要是这样写呢？这样写O(n)我直接不会说了
public in isPowerOfTwo(int x)
{
while (((x & 1) == 0) && x > 1)
x >>= 1;
return (x == 1);
}

b*r2010-04-30 07:04

8 楼

false bottom confirmed..

e*i2010-04-30 07:04

9 楼

(x & (x-1)) == 0

【在 m**r 的大作中提到】

: public int isPowerOfTwo(int x)
: {
: return(
: x == 1 || x == 2 || x == 4 || x == 8 || x == 16 || x == 32 ||
: x == 64 || x == 128 || x == 256 || x == 512 || x == 1024 ||
: x == 2048 || x == 4096 || x == 8192 || x == 16384 ||
: x == 32768 || x == 65536 || x == 131072 || x == 262144 ||
: x == 524288 || x == 1048576 || x == 2097152 ||
: x == 4194304 || x == 8388608 || x == 16777216 ||
: x == 33554432 || x == 67108864 || x == 134217728 ||