Merge pull request #37 from pezy/master

fixed some bugs.
Update ex6_25_26.cpp
Update ex6_25_26.cpp
Merge pull request #38 from shbling/patch-2

Improved naming: ex6_25_26.cpp
Update README.md
Merge pull request #40 from shbling/patch-5

fix bug : Exercise 6.34.
Improved Ex 6.34 ,thx @shbling for reporting.