BZOJ 3689 异或之

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<queue>
#define maxn 100050
using namespace std;
int n,k,a[maxn],tree[maxn*32][2],sum[maxn*32],root,tot,s[maxn*10],top=0;
struct status
{
int val,pos,k;
status (int val,int pos,int k):val(val),pos(pos),k(k) {}
status () {}
friend bool operator < (const status &x,const status &y)
{
return x.val>y.val;
}
};
priority_queue <status> q;
void insert(int &now,int val,int bit)
{
if (!now) now=++tot;sum[now]++;
if (bit==-1) return;
int nb=(val&(1<<bit));
insert(tree[now][(nb>0)],val,bit-1);
}
int ask(int now,int val,int k,int bit)
{
if (bit==-1) return 0;
int nb=val&(1<<bit);
if (!nb)
{
if (sum[tree[now][0]]>=k) return ask(tree[now][0],val,k,bit-1);
else return ask(tree[now][1],val,k-sum[tree[now][0]],bit-1)+(1<<bit);
}
else
{
if (sum[tree[now][1]]>=k) return ask(tree[now][1],val,k,bit-1);
else return ask(tree[now][0],val,k-sum[tree[now][1]],bit-1)+(1<<bit);
}
}
int main()
{
scanf("%d%d",&n,&k);
for (int i=1;i<=n;i++)
{
scanf("%d",&a[i]);
insert(root,a[i],30);
}
for (int i=1;i<=n;i++) q.push(status(ask(root,a[i],2,30),i,2));
for (int i=1;i<=2*k;i++)
{
status now=q.top();q.pop();
s[++top]=now.val;q.push(status(ask(root,a[now.pos],now.k+1,30),now.pos,now.k+1));
}
for (int i=1;i<=2*k;i+=2) printf("%d ",s[i]);
return 0;
}