Merge pull request #2 from ds-sww/master

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size,isEmpty,get,add,remove
fix bugs of remove()
first homework
first commit
修改了文件目录
抽象出了checkSize方法
发现remove忘记返回值了...
assignment2 Problems
test branch
Merge branch 'master' of https://github.com/ds-sww/codebase
assiment3 beta
clean up
clean up
BST
RBTree
commit by 13301730309
sommit by 13307130309
improved assignment1
delete problem-0929.pdf