BZOJ 2843 极地旅行社

题目链接

https://www.lydsy.com/JudgeOnline/problem.php?id=2843

题解

裸的不能再裸的LCT。

代码

#include <cstdio>
#include <algorithm>

int read()
{
  int x=0,f=1;
  char ch=getchar();
  while((ch<'0')||(ch>'9'))
    {
      if(ch=='-')
        {
          f=-f;
        }
      ch=getchar();
    }
  while((ch>='0')&&(ch<='9'))
    {
      x=x*10+ch-'0';
      ch=getchar();
    }
  return x*f;
}

const int maxn=30000;

struct node
{
  node *son[2],*fa;
  int sum,val,rev;
};

int n,m,cnt;
char s[10];
node tnode[maxn+10];

node* newnode(int val)
{
  node *x=&tnode[++cnt];
  x->fa=x->son[0]=x->son[1]=NULL;
  x->sum=x->val=val;
  x->rev=0;
  return x;
}

namespace lct
{
  int pushdown(node *x)
  {
    if(x->rev)
      {
        std::swap(x->son[0],x->son[1]);
        if(x->son[0]!=NULL)
          {
            x->son[0]->rev^=1;
          }
        if(x->son[1]!=NULL)
          {
            x->son[1]->rev^=1;
          }
        x->rev=0;
      }
    return 0;
  }

  int updata(node *x)
  {
    x->sum=x->val;
    if(x->son[0]!=NULL)
      {
        x->sum+=x->son[0]->sum;
      }
    if(x->son[1]!=NULL)
      {
        x->sum+=x->son[1]->sum;
      }
    return 0;
  }

  int t(node *x)
  {
    return x==x->fa->son[1];
  }

  int isroot(node *x)
  {
    if(x->fa==NULL)
      {
        return 1;
      }
    if((x->fa->son[0]!=x)&&(x->fa->son[1]!=x))
      {
        return 1;
      }
    return 0;
  }

  int rotate(node *x)
  {
    node *f=x->fa;
    pushdown(f);
    pushdown(x);
    int k=t(x);
    x->fa=f->fa;
    if(!isroot(f))
      {
        f->fa->son[t(f)]=x;
      }
    f->son[k]=x->son[!k];
    if(x->son[!k]!=NULL)
      {
        x->son[!k]->fa=f;
      }
    f->fa=x;
    x->son[!k]=f;
    updata(f);
    updata(x);
    return 0;
  }

  int splayroot(node *x)
  {
    while(!isroot(x))
      {
        node *f=x->fa;
        if(isroot(f))
          {
            rotate(x);
          }
        else if(t(f)==t(x))
          {
            rotate(f);
            rotate(x);
          }
        else
          {
            rotate(x);
            rotate(x);
          }
      }
    return 0;
  }

  int access(node *x)
  {
    node *last=NULL;
    while(x!=NULL)
      {
        splayroot(x);
        pushdown(x);
        x->son[1]=last;
        updata(x);
        last=x;
        x=x->fa;
      }
    return 0;
  }

  int makeroot(node *x)
  {
    access(x);
    splayroot(x);
    x->rev^=1;
    return 0;
  }

  int link(node *x,node *y)
  {
    makeroot(x);
    node *f=y;
    while(f->fa!=NULL)
      {
        f=f->fa;
      }
    if(f==x)
      {
        return -1;
      }
    makeroot(y);
    y->fa=x;
    return 0;
  }

  int getsum(node *x,node *y)
  {
    makeroot(x);
    node *f=y;
    while(f->fa!=NULL)
      {
        f=f->fa;
      }
    if(f!=x)
      {
        return -1;
      }
    access(y);
    splayroot(y);
    return y->sum;
  }

  int modify(node *x,int v)
  {
    splayroot(x);
    x->val=v;
    updata(x);
    return 0;
  }
}

int main()
{
  n=read();
  for(int i=1; i<=n; ++i)
    {
      int v=read();
      newnode(v);
    }
  m=read();
  while(m--)
    {
      scanf("%s",s);
      int a=read(),b=read();
      if(s[0]=='b')
        {
          puts(lct::link(&tnode[a],&tnode[b])?"no":"yes");
        }
      else if(s[0]=='p')
        {
          lct::modify(&tnode[a],b);
        }
      else
        {
          int ans=lct::getsum(&tnode[a],&tnode[b]);
          if(ans==-1)
            {
              puts("impossible");
            }
          else
            {
              printf("%d\n",ans);
            }
        }
    }
  return 0;
}