机试练习总结05：快速幂O(logn)

int Plog(int x,int n)
{
    int y,y0;
    if(n==1)
        y=x;
    else{
        y0=Plog(x,n/2);
        y=y0*y0;
        if(n%2!=0)
            y=y*x;
    }
    return y;
}