Use Custom Header File to Facilitate Local Debugging

Printing out information is probably the fastest way to debug in competitive programming, but you have to commenting out these lines before submitting, which is time-consuming and error-prone. Printing to stderr is better but it can slow your program down. We can solve this by using pre-written printing functions combining with #ifdef to differentiate local and judge environment.

For printing function I’m using pretty printer which does a really nice job. Then add the line below to your code and you can use de() to print things and don’t have to worry about messing up your output.

#ifdef LOCAL
#include<pprint.hpp> // https://github.com/p-ranav/pprint
pprint::PrettyPrinter _printer(std::cerr);
#define de(...) _printer.compact(true).print('[', #__VA_ARGS__,"] =", __VA_ARGS__)
#define de2(...) _printer.compact(false).print('[', #__VA_ARGS__,"] =", __VA_ARGS__)
#else
#define de(...)
#define de2(...)
#endif

Note that you need to add the directory where your pprint.hpp is to the CPLUS_INCLUDE_PATH environmental variable, or use the -I flag while compiling, or just put pprint.hpp inside your system include directory.

If you think the above code is too long, you can put this part:

#ifdef LOCAL
#include<pprint.hpp> // https://github.com/p-ranav/pprint
pprint::PrettyPrinter _printer(std::cerr);
#define de(...) _printer.compact(true).print('[', #__VA_ARGS__,"] =", __VA_ARGS__)
#define de2(...) _printer.compact(false).print('[', #__VA_ARGS__,"] =", __VA_ARGS__)
#endif

in your stdc++.h, and only leave this part in your code:

#ifndef LOCAL
#define de(...)
#define de2(...)
#endif

Use -DLOCAL flag while compiling to define LOCAL, you can use other word but make sure it’s not defined in the judge.