The 2018 ACM-ICPC Asia Qingdao Regional Contest【 K XOR Clique】

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XOR Clique

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Time Limit: 1 Second      Memory Limit: 65536 KB

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BaoBao has a sequence . He would like to find a subset  of  such that ,  and  is maximum, where  means bitwise exclusive or.

Input

There are multiple test cases. The first line of input contains an integer , indicating the number of test cases. For each test case:

The first line contains an integer  (), indicating the length of the sequence.

The second line contains n integers:  (), indicating the sequence.

It is guaranteed that the sum of  in all cases does not exceed .

Output

For each test case, output an integer denoting the maximum size of .

Sample Input

3
3
1 2 3
3
1 1 1
5
1 2323 534 534 5

Sample Output

2
3

题解：给定 n 个整数，求一个集合，是的集合中的任意两个数的异或值小于这两个数。很容易发现当且仅当两个数字最高位二进制相同的时候才满足条件，即为相同二进制最高位的数字数量。

#include <bits/stdc++.h>
using namespace std;
const int maxn = 100005;
int a[33];
int main() {
	int t, n;
	scanf("%d", &t);
	while(t--) {
        scanf("%d", &n);
        int x;
        memset(a, 0, sizeof a);
        for(int i = 0; i < n; i++) {
            scanf("%d", &x);
            int cnt = 0;
            while(x > 0) {
                x/=2;
                cnt++;
            }
            a[cnt]++;
        }
        sort(a,a+33);
        reverse(a,a+33);
        printf("%d\n", a[0]);
	}
	return 0;
}