Submit first week & second week homework#25

Merged

DonaldY merged 6 commits intoDonaldY:masterfrom

denglitong:master

Mar 19, 2017

Commits on Mar 19, 2017

finish first week and second week homework
beyondself
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add first week homework untrancked files
beyondself
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delete unneed dir
beyondself
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format codes
beyondself
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add BinaryTreeNode and testcase
beyondself
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format codes
beyondself
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