做这题要知道一个技巧是可以用Trie树来查找与一个数异或第K大/小的数字.
套一个堆,这题就做完了.
1 #include<cstdio> 2 #include<algorithm> 3 #include<queue> 4 using namespace std; 5 #define ll long long 6 #define FILE "dealing" 7 #define up(i,j,n) for(int i=j;i<=n;i++) 8 #define db long double 9 #define pii pair<int,int> 10 #define pb push_back 11 #define mem(a,L) memset(a,0,sizeof(int)*(L+1)) 12 template<class T> inline bool cmin(T& a,T b){return a>b?a=b,true:false;} 13 template<class T> inline bool cmax(T& a,T b){return a<b?a=b,true:false;} 14 template<class T> inline T squ(T a){return a*a;} 15 const ll maxn=2000100+10,inf=1e9+10,limit=1e7; 16 int read(){ 17 int x=0,f=1,ch=getchar(); 18 while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();} 19 while(ch>='0'&&ch<='9')x=(x<<1)+(x<<3)+ch-'0',ch=getchar(); 20 return x*f; 21 } 22 int n,K,a[maxn]; 23 int cnt,c[maxn][2],fa[maxn],siz[maxn],rt; 24 void updata(int o){siz[o]=siz[c[o][0]]+siz[c[o][1]];} 25 void add(int& o,int x,int dep){ 26 if(!o)o=++cnt; 27 if(dep==-1){ 28 siz[o]++; 29 return; 30 } 31 if(x&(1<<dep))add(c[o][1],x,dep-1); 32 else add(c[o][0],x,dep-1); 33 updata(o); 34 } 35 int vis[maxn]; 36 int find(int pre,int o,int val,int k,int dep){ 37 if(dep==-1)return val; 38 int d=(pre&(1<<dep))?1:0; 39 if(siz[c[o][d]]>=k)return find(pre,c[o][d],val,k,dep-1); 40 else return find(pre,c[o][d^1],val|(1<<dep),k-siz[c[o][d]],dep-1); 41 } 42 priority_queue<pii ,vector<pii >,greater<pii > > q; 43 int main(){ 44 freopen(FILE".in","r",stdin); 45 freopen(FILE".out","w",stdout); 46 n=read(),K=read()*2; 47 up(i,1,n)a[i]=read(),add(rt,a[i],30); 48 up(i,1,n)vis[i]=1; 49 up(i,1,n)q.push(make_pair(find(a[i],rt,0,++vis[i],30),i)); 50 up(t,1,K){ 51 pii k=q.top();q.pop(); 52 int i=k.second,key=k.first; 53 if(t&1)printf("%d ",key); 54 q.push(make_pair(find(a[i],rt,0,++vis[i],30),i)); 55 } 56 57 return 0; 58 }