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课程地址
http://v.163.com/special/opencourse/algorithms.html
今天课程地址:
http://open.163.com/movie/2010/12/G/F/M6UTT5U0I_M6V2T1JGF.html
讨论performance
Analysis of Algorithms: the study of computer program performance ans resource usage.
Thinking: What is more important than performance?
Functionality, modularity, user-friendliness, security...
Then why study algs and perf?
performance is like the "money", you can buy other stuff...这个有点不懂，讨论一下
Problem sorting
Insertion sort
每次保证在第i位置之前的都是sort好的
8 2 4 9 3 6 i = 1
2 8 4 9 3 6 i = 2
2 4 8 9 3 6 i = 3
2 4 8 9 3 6 i = 4
2 3 4 8 9 6 i = 5
2 3 4 6 8 9 done
Running time analysis
wrost case, ave case, best case
BIG IDEA: Asymptotc analysis 渐进分析
Θ notation, 比的是n在无限大时的情况～所以n^2肯定比n^3快哒。
Wrost case：
Θ（n^2）
Merge sort A[1,..., n]
1, if n =1, done
2, recursively sort A[1,..., n/2] and A[n/2 + 1, ..., n]
3, merge 2 sorted lists
T(n) = 2T(n/2) + Θ(n) if n > 1
T(n) = cn*lgn + Θ(n) = Θ(nlgn) c代表常数
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原文地址：http://www.cnblogs.com/wnan42/p/4676202.html
