Merge pull request #3 from Mooophy/master

SYN
Fix some bugs
Merge pull request #62 from huangjuncmj/patch-1

Fix some bugs for ch09/ex9_26.cpp
ex17.14.15.16
test
fix bug
Merge pull request #63 from Queequeg92/master

add  ex17.14.15.16
Fix note information
Merge pull request #65 from Queequeg92/master

Fix note information
Update ex9_13.cpp
Update ex9_13.cpp
Merge pull request #67 from shbling/patch-1

Update ex9_13.cpp
better format
Update ex9_15_16_17.cpp
Merge pull request #68 from shbling/patch-4

Update ex9_15_16_17.cpp
ex18.12.13.14
Merge remote-tracking branch 'origin/master'
Merge pull request #69 from Queequeg92/master

add solutions for ex18.12.13.14.
Merge pull request #4 from Mooophy/master

SYN
ex18.15.16.17