Solve recurrence

Solve recurrences

1、substitution method 代换法

a、guess  the form of  the solution

b、verify by induction（归纳）

c、solve for constants

2、recursion-tree  method

a、draw a general picture

b、sum level by level

3、master method

seem as the application of recursion tree  only applies to a particular family of recurrences such as 

   T(n)= aT(n/b)+f(n)  a>=1,b>1    f(n)  should be asymptomatically postive  渐进趋正

compare f(n) with nlogb a