c++cmathlong-integercmath

What is 1LL or 2LL in C and C++?

I was looking at some of the solutions in Google Code Jam and some people used this things that I had never seen before. For example,

2LL*r+1LL

What does 2LL and 1LL mean?

Their includes look like this:

#include <math.h>
#include <algorithm>
#define _USE_MATH_DEFINES

or 

#include <cmath>
Solution

  • The LL makes the integer literal of type long long.

    So 2LL, is a 2 of type long long.

    Without the LL, the literal would only be of type int.

    This matters when you're doing stuff like this:

    1   << 40
1LL << 40

    With just the literal 1, (assuming int to be 32-bits, you shift beyond the size of the integer type -> undefined behavior). With 1LL, you set the type to long long before hand and now it will properly return 2^40.