C++ :

#include<stdio.h>
#include<math.h>
int main()
{
    int i,a,b,x,y,m,n,q;
    double p,min=1;
    scanf("%d%d",&a,&b);
    for(i=2;i<=32767;i++)
    {
        p=(double)i*a/b;
        q=(int)p;
        if(fabs(p-q)<=1e-6)
            x=q-1;
        else if(p-q<=q+1-p)
            x=q;
        else
            x=q+1;                //四舍五入，加0.5会出现精度问题
        y=i;
        if(fabs((double)x/y-(double)a/b)<min)
        {
            min=fabs((double)x/y-(double)a/b);
            m=x;
            n=y;
        }
    }
    for(i=2;i<=32767;i++)
        if(m%i==0&&n%i==0)
        {
            m/=i;
            n/=i;
        }
        printf("%d %d",m,n);
        return 0;
}