Question

I am writing a program in C++ where I have to calculate the value of n^n where 1<=n<=10^9. But even if I use long long type to store the result, the answer is calculated just till n=15.
At n=16, a floating point exception arises and and after that results show negative values. Can anybody tell me what is wrong with the code?

long long c;

c=(long long)n;
for(int i=2;i<=n;i++)
   c*=n;

 cout<<c<<endl;

Answer 1

If you are getting negative values then you are overflowing the variable. You need to use a data type that has a larger range, one that is sufficient to hold the numbers you wish to calculate. If your system does not come with such a data type (and I rather suspect that long long is as big as you will get) then you will need to use a bignum class.

Looking more closely at the numbers in your question, I think that many standard bignum classes will not be able to calculate nⁿ for n=10⁹. Are you sure you wrote the problem down correctly?