【HDU 3949】XOR

XOR

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 1459    Accepted Submission(s): 438

Problem Description

XOR is a kind of bit operator, we define that as follow: for two binary base number A and B, let C=A XOR B, then for each bit of C, we can get its value by check the digit of corresponding position in A and B. And for each digit, 1 XOR 1 = 0, 1 XOR 0 = 1, 0 XOR 1 = 1, 0 XOR 0 = 0. And we simply write this operator as ^, like 3 ^ 1 = 2,4 ^ 3 = 7. XOR is an amazing operator and this is a question about XOR. We can choose several numbers and do XOR operatorion to them one by one, then we get another number. For example, if we choose 2,3 and 4, we can get 2^3^4=5. Now, you are given N numbers, and you can choose some of them(even a single number) to do XOR on them, and you can get many different numbers. Now I want you tell me which number is the K-th smallest number among them.

 

Input

First line of the input is a single integer T(T<=30), indicates there are T test cases.
For each test case, the first line is an integer N(1<=N<=10000), the number of numbers below. The second line contains N integers (each number is between 1 and 10^18). The third line is a number Q(1<=Q<=10000), the number of queries. The fourth line contains Q numbers(each number is between 1 and 10^18) K1,K2,......KQ.

 

Output

For each test case,first output Case #C: in a single line,C means the number of the test case which is from 1 to T. Then for each query, you should output a single line contains the Ki-th smallest number in them, if there are less than Ki different numbers, output -1.

 

Sample Input

221 241 2 3 431 2 351 2 3 4 5

 

Sample Output

Case #1:123-1Case #2:0123-1
Hint
If you choose a single number, the result you get is the number you choose.Using long long instead of int because of the result may exceed 2^31-1.
 

 

Author

elfness

 

Source

2011 Multi-University Training Contest 11 - Host by UESTC

首先高斯消元，求第k大就是把k二进制拆分，是1的位的对应数异或就是答案。

对于0要特判。

#include <iostream>#include <algorithm>#include <cstdio>#include <cstring>#include <cstdlib>#define LL long longusing namespace std;int now,k,n,m,T;LL a[10005];void Gauss(){now=1,k=62;while (k--){for (int i=now;i<=n;i++)if (a[i]&(1LL<<k)){swap(a[i],a[now]);for (int j=1;j<=n;j++)if (j!=now&&(a[j]&(1LL<<k))) a[j]^=a[now];now++;break;}}now--;}LL Calc(LL k){LL ans;ans=0LL;if (now<n){if (k==1) return 0;k--;}if (k>=(1LL<<now)) return -1;for (int i=now;k;i--,k>>=1){if (k&1LL)ans^=a[i];}return ans;}int main(){scanf("%d",&T);for (int t=1;t<=T;t++){scanf("%d",&n);for (int i=1;i<=n;i++)scanf("%lld",&a[i]);Gauss();printf("Case #%d:\n",t);scanf("%d",&m);while (m--){LL x;scanf("%lld",&x);printf("%lld\n",Calc(x));}}return 0;}

感悟：

对xor理解的一道好题！