代码

int binary_search(unsigned *a,int n,register unsigned x)
{
	register unsigned*p=a+1ll*n*x/a[n-1];
	if(x<=*p)
	{
		register int t=4;
		for(;p[-t]>x;t<<=1);
		for(;t>>=1;)
		{
			p[-t]>=x?p-=t:0;
			t>>=1;
			p[-t]>=x?p-=t:0;
		}
		return p-a;
	}
	else
	{
		register int t=4;
		for(;p[t]<x;t<<=1);
		for(;t>>=1;)
		{
			p[t]<=x?p+=t:0;
			t>>=1;
			p[t]<=x?p+=t:0;
		}
		return p-a;
	}
}

评测结果