Math basic

Constant	5
Poly logarithmetic	(logn)5
Polynomial	n5
Exponential	25n
Exp	2n5
Double Exp	225n

  

linear	O(n)
Quadratic	O(n2)
Cubic	O(n3)

 

 

 

高斯求和

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1	2	3	4	5	...	...	n	=	n(n+1)/2
n	n-1	n-2	n-3	n-4	...	...	1	=

 

 

几何求和

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1	2	4	8	...	2n	=	2(n+1)-1
1	q	q2	q3	...	qn	=	(qn+1-1)/(q-1): proof: 1+q+q2+q3+...+qn           = Sn     q+q2+q3+...+qn+qn+1 = qSn - qn+1 - 1 = (q-1)Sn

 

Harmonic sum:

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1+1/2+1/3+1/4+...+1/n