50. Pow(x, n)

Implement pow(x, n).

double myPow(double x, int n) {
    unsigned int m = n;
    bool flag = false;
    double ans = 1;
    if(n < 0)
    {
        flag = true;
        m = -n;
    }
    while(m)
    {
        if(m & 1)
            ans *= x;
        x = x * x;
        m = m>>1;
    }
    return flag ? 1/ans : ans;
}