I too hate this kind of precision errors in C++.

I had same problem in past contest.

use this pow("m" is mod in the code,it is good for calculating (x^y)%m ,remove it if you don't use it):

link

i think because the pow function must work with doubles it is O(N) instead of O(log(N))(if isn't tell me).

because O(log(N)) pow is very useful try to use your pow with O(log(N))!

thanx!

Here my code with builtin fast_power which work in O(log(N))

#include "bits/stdc++.h"
#include <ext/numeric>
using namespace std;
using namespace __gnu_cxx;
int main()
{
   cout<<power(2,3);
}

In C++, you can write a user-defined function long long pow10(int n) to compute and return the nth power of 10 for some non-negative integer 0 ≤ n ≤ 18 using the string-to-long-long conversion function string::stoll()as follows.

inline long long pow10(int n)    
{
    return stoll("1"+string(n,'0'));
}

string(n,'0') constructs an n-character string filled with decimal zeros. When concatenated properly with "1", the sought string representation of 10ⁿ is generated.

You may use the C++ preprocessor to write the return expression as a #define macro as follows.

#define pow10(n) stoll("1"+string(n,'0'))

Using ceil( pow(base,exponent) ) worked for me.

pow(x, y) is most likely implemented as exp(y * log(x)) which can go off for surprisingly small integral arguments. This manifests itself in a particularly pathological way if the result is truncated to an integer.

The moral of the story is to avoid the pow function when working in integer arithmetic.

In case of resulting an int value try using binary exponentiation instead of pow() function.... It is more reliable than pow() function..
you can see the here...
Hope that this will help you to not getting this type of error again....