while (++i<=r)
{ a[i]+=t;
if (++i<=r) a[i]+=t;
if (++i<=r) a[i]+=t;
if (++i<=r) a[i]+=t;
if (++i<=r) a[i]+=t;
if (++i<=r) a[i]+=t;
if (++i<=r) a[i]+=t;
if (++i<=r) a[i]+=t;
if (++i<=r) a[i]+=t;
}
这样也可以循环展开????