add chapter 30~31
Update 30.0~31.0.md
Update 30.0~31.0.md
Update 30.0~31.0.md
Update preface.md
Merge remote-tracking branch 'upstream/master'
update
Update preface.md
update
update
remove preface.md.bak
Delete .directory
update
add chapter 36
fix some typos in README.md
Add bit version for char sequence intersection.
Update chapter01.cpp

Validate the input argument "str". If it is not correctly set (str.length() < 1), just return the function . And if it contains only one character (str.length() == 1), again we just return the function.
Merge remote-tracking branch 'upstream/master'
Merge pull request #66 from wuchong/master

add chapter 36~37 again
Merge pull request #68 from ailurus1991/working

fix some typos in README.md