正题

题目链接:https://www.luogu.com.cn/problem/P3850

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题目大意

一个书架上有$n$本书，进行$m$次插入操作，然后$q$次询问一个位置上的书。

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解题思路

用$Splay$进行插入操作，然后直接查询即可

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$code$

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
const int N=2e5;
int n,m,root;char s[N][15];
int tot,t[N][2],siz[N],fa[N];
void PushUp(int x)
{siz[x]=siz[t[x][0]]+siz[t[x][1]]+1;return;}
bool Direct(int x)
{return t[fa[x]][1]==x;}
void Connect(int x,int y,int son)
{t[x][son]=y;fa[y]=x;return;}
void Rotate(int x){int y=fa[x],z=fa[fa[x]];int xs=Direct(x),ys=Direct(y);int k=t[x][xs^1];Connect(y,k,xs);Connect(x,y,xs^1);Connect(z,x,ys);PushUp(y);PushUp(x);return;
}
void Splay(int x,int f){while(fa[x]!=f){int up=fa[x];if(fa[up]==f)Rotate(x);else if(Direct(x)==Direct(up))Rotate(up),Rotate(x);else Rotate(x),Rotate(x);}return;
}
int Find(int x,int k){if(siz[t[x][0]]>=k)return Find(t[x][0],k);if(siz[t[x][0]]+1==k)return x;return Find(t[x][1],k-siz[t[x][0]]-1);
}
int main()
{scanf("%d",&n);siz[1]=1;for(int i=1;i<=n;i++){scanf("%s",s[i+1]);fa[i]=i+1;t[i+1][0]=i;PushUp(i+1);}fa[n+1]=n+2;t[n+2][0]=n+1;PushUp(n+2);root=tot=n+2;scanf("%d",&m);while(m--){scanf("%s",s[++tot]);int l;scanf("%d",&l);l++;int x=Find(root,l),y=Find(root,l+1);Splay(x,0);Splay(y,x);t[y][0]=tot;fa[tot]=y;siz[tot]=1;Splay(tot,0);root=tot;}scanf("%d",&m);while(m--){int l;scanf("%d",&l);l++;int x=Find(root,l),y=Find(root,l+2);Splay(x,0);Splay(y,x);root=x;printf("%s\n",s[t[y][0]]);}
}