题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=3949
题意：给出一个长度为n的数列A。选出A的所有子集（除空集外）进行抑或得到2^n-1个数字，去重排序得到B。给出一个数K，询问在B中第K个数字是多少？
思路：首先看做n个二进制的数字进行高斯消元，得到k个线性无关的数字。然后由这k个线性无关的数字得到第K个数字。这里不能选择空集，因此对于B中是否存在0要进行特判。
#include <iostream>
#include <cstdio>
#include <string.h>
#include <algorithm>
#include <cmath>
#include <vector>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <map>
#include <ctype.h>
#include <time.h>
#define abs(x) ((x)>=0?(x):-(x))
#define i64 long long
#define u32 unsigned int
#define u64 unsigned long long
#define clr(x,y) memset(x,y,sizeof(x))
#define CLR(x) x.clear()
#define ph(x) push(x)
#define pb(x) push_back(x)
#define Len(x) x.length()
#define SZ(x) x.size()
#define PI acos(-1.0)
#define sqr(x) ((x)*(x))
#define MP(x,y) make_pair(x,y)
#define EPS 1e-10
#define FOR0(i,x) for(i=0;i<x;i++)
#define FOR1(i,x) for(i=1;i<=x;i++)
#define FOR(i,a,b) for(i=a;i<=b;i++)
#define FORL0(i,a) for(i=a;i>=0;i--)
#define FORL1(i,a) for(i=a;i>=1;i--)
#define FORL(i,a,b)for(i=a;i>=b;i--)
#define rush() int CC;for(scanf("%d",&CC);CC--;)
#define Rush(n) while(scanf("%d",&n)!=-1)
using namespace std;
void RD(int &x){scanf("%d",&x);}
void RD(i64 &x){scanf("%I64d",&x);}
void RD(u64 &x){scanf("%I64u",&x);}
void RD(u32 &x){scanf("%u",&x);}
void RD(double &x){scanf("%lf",&x);}
void RD(int &x,int &y){scanf("%d%d",&x,&y);}
void RD(i64 &x,i64 &y){scanf("%lld%lld",&x,&y);}
void RD(u32 &x,u32 &y){scanf("%u%u",&x,&y);}
void RD(double &x,double &y){scanf("%lf%lf",&x,&y);}
void RD(double &x,double &y,double &z){scanf("%lf%lf%lf",&x,&y,&z);}
void RD(int &x,int &y,int &z){scanf("%d%d%d",&x,&y,&z);}
void RD(i64 &x,i64 &y,i64 &z){scanf("%lld%lld%lld",&x,&y,&z);}
void RD(u32 &x,u32 &y,u32 &z){scanf("%u%u%u",&x,&y,&z);}
void RD(char &x){x=getchar();}
void RD(char *s){scanf("%s",s);}
void RD(string &s){cin>>s;}
void PR(int x) {printf("%d\n",x);}
void PR(int x,int y) {printf("%d %d\n",x,y);}
void PR(i64 x) {printf("%I64d\n",x);}
void PR(i64 x,i64 y) {printf("%lld %lld\n",x,y);}
void PR(u32 x) {printf("%u\n",x);}
void PR(u64 x) {printf("%llu\n",x);}
void PR(double x) {printf("%.10lf\n",x);}
void PR(double x,double y) {printf("%.5lf %.5lf\n",x,y);}
void PR(char x) {printf("%c\n",x);}
void PR(char *x) {printf("%s\n",x);}
void PR(string x) {cout<<x<<endl;}
void upMin(int &x,int y) {if(x>y) x=y;}
void upMin(i64 &x,i64 y) {if(x>y) x=y;}
void upMin(double &x,double y) {if(x>y) x=y;}
void upMax(int &x,int y) {if(x<y) x=y;}
void upMax(i64 &x,i64 y) {if(x<y) x=y;}
void upMax(double &x,double y) {if(x<y) x=y;}
const int mod=10086;
const i64 inf=((i64)1)<<60;
const double dinf=1e10;
const int INF=100000000;
const int N=100005;
int n,m,flag;
i64 a[N];
int Gauss()
{
flag=1;
int i,j=0,k;
i64 p=1;
for(i=63;i>=0;i--)
{
for(k=j;k<n;k++) if(a[k]&(p<<i)) break;
if(k>=n) continue;
swap(a[j],a[k]);
for(k=0;k<n;k++) if(j!=k&&(a[k]&(p<<i)))
{
a[k]^=a[j];
if(a[k]==0) flag=0;
}
j++;
}
return j;
}
int main()
{
int num=0;
rush()
{
RD(n);
int i;
FOR0(i,n) RD(a[i]);
int k=Gauss();
RD(m);
printf("Case #%d:\n",++num);
i64 K,p=1,ans;
while(m--)
{
RD(K);
if(K>(p<<k)-flag) puts("-1");
else if(!flag&&K==1) puts("0");
else
{
if(!flag) K--;
ans=0;
for(i=0;i<k;i++) if(K>=(p<<(k-i-1)))
{
K-=(p<<(k-i-1));
ans^=a[i];
if(K==0) break;
}
PR(ans);
}
}
}
}