Merge pull request #4 from ds-sww/master

``
Merge https://github.com/whimsycwd/codebase into assignment6
assignment6.5
assignment7
Merge pull request #5 from ds-sww/master

~
Assignment7 completed
assignment8.5
Assignment8.5 Init.
'前一个过了，后一个要是tle也就算了，但是他说我wa，我觉得和第一个差不多啊，也找不出错，谁能告诉我问题'
poj 2255
poj 1240
assignment7
Assignment 6
Assignment 7
Add assignment7
13307130280_assignment8
7
用生成树的方法写了遍2255(本来想不用栈结果还是用了...)
Merge pull request #392 from spirizonx/assignment8.5

12307130066_XuanYuan_Assignment8.5 [Init.]
Merge pull request #390 from xiaoguai0992/assignment8.5

13307130389_KangzhengGu_assignment8.5