玲珑学院OJ 1028 - Bob and Alice are playing numbers 字典树，dp

Posted 2020-08-07 shuguangzw

http://www.ifrog.cc/acm/problem/1028

题解处：http://www.ifrog.cc/acm/solution/4

#include <cstdio>
#include <cstring>
#include <queue>
#include <cmath>
#include <algorithm>
using namespace std;
typedef long long LL;
const int N = 1e5 + 5;
const double eps = 1e-9;
const double INF = 1e12;
int ch[N*60][2],cnt[N*60],tot,a[N],n,T,op,kase;
bool dp[(1<<21)+5];
inline int newnode(){
  ++tot;
  ch[tot][0]=ch[tot][1]=-1;
  cnt[tot]=0;
  return tot;
}
void insert(int x){
  int ptr = 0;
  for(int i=20;i>=0;--i){
    int nx = (x&(1<<i))?1:0;
    if(ch[ptr][nx]==-1)
      ch[ptr][nx]=newnode();
    ptr = ch[ptr][nx];++cnt[ptr];
  }
}
void Union(int &x,int y){
  if(y==-1)return;
  if(x==-1)x = newnode();
  cnt[x]+=cnt[y];
  Union(ch[x][0],ch[y][0]);
  Union(ch[x][1],ch[y][1]);
}
int ask_xor(int x){
   int ret=0,ptr=0;
   for(int i=20;i>=0;--i){
      int nx = (x&(1<<i))?1:0;
      if(ch[ptr][nx^1]!=-1){
        ret|=(1<<i);
        ptr=ch[ptr][nx^1];
      }
      else ptr=ch[ptr][nx];
      if(ptr==-1)break;
   }
   return ret;
}
int ask_and(){
  int ret=0,ptr=0;
  for(int i=20;i>=0;--i){
    if(ch[ptr][1]!=-1&&cnt[ch[ptr][1]]>=2)
      ret|=(1<<i);
    else Union(ch[ptr][1],ch[ptr][0]);
    ptr=ch[ptr][1];
  }
  return ret;
}
void ask_or(){
  memset(dp,false,sizeof(dp));
  for(int i=1;i<=n;++i)dp[a[i]]=true;
  for(int i=(1<<20);i>=1;--i){
    for(int j=0;j<=20;++j)
      if(!(i&(1<<j)))dp[i]|=dp[i|(1<<j)];
  }
  int ret=0,p=0;
  int tmp[25];
  for(int i=1;i<=n;++i){
    p=0;
    for(int j=20;j>=0;--j)
      if(!(a[i]&(1<<j)))tmp[++p]=(1<<j);
    int x=0;
    for(int j=1;j<=p;++j){
      if(dp[x|tmp[j]])x|=tmp[j];
    }
    ret=max(ret,x|a[i]);
  }
  printf("%d\\n",ret);
}
int main(){
  scanf("%d",&T);
  while(T--){
    scanf("%d%d",&n,&op);
    tot=-1;newnode();int ret_xor=0;
    for(int i=1;i<=n;++i){
      scanf("%d",&a[i]);
      if(op==2)ret_xor=max(ret_xor,ask_xor(a[i]));
      insert(a[i]);
    }
    printf("Case #%d: ",++kase);
    if(op==2)printf("%d\\n",ret_xor);
    else if(op==1)printf("%d\\n",ask_and());
    else ask_or();
  }
  return 0;
}

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