[HDU3949] 线性基+xor第k大

[HDU3949]

• zbl zbl
• 把线性基中非零元素排出来
• 按照k的二进制分解选择
• 如果线性基外有元素k--
• 正确性显然，类比k的二进制表示

Code 

---

#include<bits/stdc++.h>
#define rep(i,a,b) for(ll i=(a);i<=(b);i++)
#define per(i,a,b) for(ll i=(a);i>=(b);i--)
#define ll long long
using namespace std;
const ll lim=63;
const ll N=1e5;
ll Case=0,tot,k,m,n,T;
ll a[N],b[N],val;
void insert(ll v){
	per(i,lim,0)if((v>>i)&1){
		if(a[i])v^=a[i];
		else{
			per(j,i-1,0)if((v>>j)&1)v^=a[j];
			rep(j,i+1,lim)if((a[j]>>i)&1)a[j]^=v;
			a[i]=v;break;
		}
	}
}
void work(){
	scanf("%lld",&m);
	printf("Case #%d:\n",++Case);
	while(m--){
		ll ans=0;
		scanf("%lld",&k);
		if(n!=tot)k--;
		if(k>=(1<<tot))puts("-1");
		else{
			rep(i,0,lim)if((k>>i)&1)ans^=a[i];
			printf("%lld\n",ans);
		}
	}
}
int main()
{
	scanf("%lld",&T);
	while(T--){
		memset(a,0,sizeof(a));
		memset(b,0,sizeof(b));
		tot=0;
		scanf("%lld",&n);
		rep(i,1,n)scanf("%lld",&val),insert(val);
		rep(i,0,lim)if(a[i])a[tot++]=a[i];
		work();
	}
	return 0;
}