C++ 6.0 问题

double x=0,y1=0,y2=0;
double a[4][3]={{1,3,0.5},{2,5,0.7},{3,7,0.85},{4,10,1.10}};
scanf("%f",x);
if(x<=0.5)
{
    printf("X IS BEYOND THE RANGE\n");
    return 0;
}
x=(x+1)/1;
switch(x)
{
    case 1:
        y1=a[x][1];
        y2=a[x][1];
        break;
    case 2:
        y1=a[x][1];
        y2=a[x][1];
        break;
    case 3:
        y1=a[x][1];
        y2=a[x][1];
        break;
    case 4:
        y1=a[x][1];
        y2=a[x][1];
        break;
    default:
        break;
}
基本就这个思想，自己在改一下吧