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
| 1 | 2 | 3 | 4 | 5 | ... | ... | n | = | n(n+1)/2 |
| n | n-1 | n-2 | n-3 | n-4 | ... | ... | 1 | = |
几何求和
| 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
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Harmonic sum:
1+1/2+1/3+1/4+...+1/n
