https://pintia.cn/problem-sets/1036903825309761536/problems/1041156503909756928
K XOR Clique
BaoBao has a sequence a1,a2,...,an. He would like to find a subset S of {1,2,...,n} such that ∀i,j∈S, ai⊕aj<min(ai,aj) and ∣S∣ is maximum, where ⊕ means bitwise exclusive or.
Input
There are multiple test cases. The first line of input contains an integer T, indicating the number of test cases. For each test case:
The first line contains an integer n (1≤n≤105), indicating the length of the sequence.
The second line contains n integers: a1,a2,...,an (1≤ai≤109), indicating the sequence.
It is guaranteed that the sum of n in all cases does not exceed 105.
Output
For each test case, output an integer denoting the maximum size of S.
Sample Input
3
3
1 2 3
3
1 1 1
5
1 2323 534 534 5
Sample Output
2
3
2
作者: 浙江大学竞赛命题组
单位: ACMICPC
时间限制: 500 ms
内存限制: 64 MB
代码长度限制: 32 KB
#include<stdio.h>
#include<algorithm>
using namespace std;
int main()
{
int i,j;
for(i=0;i<=16;i++)
{
for(j=0;j<=100;j++)
{
if((i^j)<min(i,j))
printf("%d %d\n",i,j);
}
}
return 0;
}
可以看出规律，符合条件的在2^n与2^(n+1)之间，所以只要求在哪个阶段中的数最多即可。
#include<stdio.h>
#include<stdlib.h>
#include<math.h>
#include<string.h>
#include<algorithm>
using namespace std;
#define N 120
int a[N];
int main()
{
int n,i,j,t,maxn,x;
scanf("%d",&t);
while(t--)
{
maxn=0;
memset(a,0,sizeof(a));
scanf("%d",&n);
for(i=1;i<=n;i++)
{
scanf("%d",&x);
for(j=0;;j++)
{
if(x>=pow(2,j)&&x<pow(2,j+1))
{
a[j]++;
maxn=max(a[j],maxn);
break;
}
}
}
printf("%d\n",maxn);
}
return 0;
}