add 4.c
add 5.c
add 6.c
Merge branch 'dev3'
update 1.c and 2.c
update 1.c and 2.c and 3.c
update 6.c
Merge branch 'master' of code.csdn.net:zh863070535/test

Conflicts:
	1.c
	2.c
update README.md