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是除3……

Posted by frkstyc at 2006-03-23 11:47:34 on Problem 2506
In Reply To:计算 (2^(n+1)+1)%3 Posted by:gemenhao at 2006-03-23 11:14:56 
> 实际为 
>   f(n) = f(n-1)+2*f(n-2)
> 得到
>   f(n) = (2*2^n+(-1)^n)/3 = (2^(n+1)+1)%3  (why?)
> 
>   if(n<62)
>  
> 
> 快速计算上面的表达式,计算2的幂用移位快
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