Get Nth power of number.

Question:
Given two integer a and b (b >= 0), please write a function to return the result of "a to the power of b".

My Anwser: (I am no sure if it is correct.)
The easiest way is recursively multiply integer a.

int power(int a, int b)
{
    if (b <= 0)
        return 1;

    return a * power(a, b-1);
}

Question:
Improve time complexity to log(n)

My Anwser: (I am no sure if it is correct.)
Consider a to the power of 15 is power(a, 8) * power(a, 4) * power(a, 2) * power(a, 1) * power(a, 0)

#include "stdafx.h"
#include 

using namespace std;

int getPower(int a, int b);
int power(int a, int b);

int _tmain(int argc, _TCHAR* argv[])
{
    int a = 2, b = 15;
 
    cout << power(a, b) << endl;

    cin.get();
    return 0;
}

int getPower(int a, int logb)
{
    if (logb <= 0)
        return 1;

    return a * getPower(a*a, logb-1);
}

int power(int a, int b)
{
    if (b == 0)
        return 1;

    int logb = 0;
    while(b>0)
    {
        logb++;
        b >>= 1;
    }

    return getPower(a, logb);
}