题面：【模板】普通平衡树

代码：

 1 #include<cstdio>
 2 #include<cstring>
 3 #include<iostream>
 4 #include<cstdlib>
 5 using namespace std;
 6 inline int rd(){
 7     int x=0,f=1;char c=getchar();
 8     while(c<'0'||c>'9'){if(c=='-')f=-1; c=getchar();}
 9     while(c>='0'&&c<='9'){x=x*10+c-'0'; c=getchar();}
10     return f*x;
11 }
12 const int maxn=(2e5)+50;
13 int N,chd[maxn][3],a,o,val[maxn],rt,x,y,z,g,pr[maxn],tot=0,siz[maxn]; 
14 inline int New_node(int a){
15     val[++tot]=a;
16     pr[tot]=rand();
17     siz[tot]=1;
18     return tot;
19 }
20 inline void Pushup(int a){
21     siz[a]=siz[chd[a][0]]+siz[chd[a][1]]+1;
22     return;
23 }
24 inline void Split(int now,int k,int &x,int &y){
25     if(!now){x=y=0; return;}
26     if(val[now]<=k){
27         x=now;
28         Split(chd[now][1],k,chd[now][1],y);
29     }
30     else{
31         y=now;
32         Split(chd[now][0],k,x,chd[now][0]);
33     }
34     Pushup(now);
35     return;
36 }
37 inline int Merge(int a,int b){
38     if(!a||!b)return (a+b);
39     if(pr[a]<pr[b]){
40         chd[a][1]=Merge(chd[a][1],b);
41         Pushup(a);
42         return a;
43     }
44     else{
45         chd[b][0]=Merge(a,chd[b][0]);
46         Pushup(b);
47         return b;
48     }
49 }
50 inline int Kth(int now,int k){
51     while(now){
52         if(k<=siz[chd[now][0]])now=chd[now][0];
53         else if(k==siz[chd[now][0]]+1)return now;
54         else k=k-siz[chd[now][0]]-1,now=chd[now][1];
55     }
56     return now;
57 }
58 int main(){
59     srand(20030304);
60     N=rd();
61     rt=0;
62     while(N--){
63         o=rd();a=rd();
64         if(o==1){
65             Split(rt,a,x,y);
66             rt=Merge(Merge(x,New_node(a)),y);
67         }
68         else if(o==2){
69             Split(rt,a,x,z);
70             Split(x,a-1,x,y);
71             rt=Merge(Merge(x,Merge(chd[y][0],chd[y][1])),z);
72         }
73         else if(o==3){
74             Split(rt,a-1,x,y);
75             printf("%d\n",siz[x]+1);
76             rt=Merge(x,y);
77         }
78         else if(o==4){
79             printf("%d\n",val[Kth(rt,a)]);    
80         }
81         else if(o==5){
82             Split(rt,a-1,x,y);
83             printf("%d\n",val[Kth(x,siz[x])]);
84             rt=Merge(x,y);
85         }
86         else{//o==6
87             Split(rt,a,x,y);
88             printf("%d\n",val[Kth(y,1)]);
89             rt=Merge(x,y);
90         }
91     }
92     return 0;
93 }

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By:AlenaNuna