A quick way to correct the indentation of c/c++ code with vim, from stackoverflow.
First install astyle, the ANSI style
apt-get install astyle
Then inside vim:
:%!astyle # astyle default mode is C/C++, this work on whole file
:%!astyle --mode=c --style=ansi -s2 # ansi C++ style, use two spaces per indent level
:1,40!astyle --mode=c --style=ansi # ansi C++ style, filter only lines 1-40