代码

int binary_search(const unsigned *a, int n, unsigned x)
{
	int l=0,r=n;
        int ans=-1;
        int mid;
        while(l<=r)
        {
                mid=(l+r)>>1;
                if(a[mid]==x) return mid;
                if(a[mid]<x) l=mid+1;
                else r=mid-1;
        }
}

评测结果