无旋treap

 #ifndef FHQTREAP_H_INCLUDED
 #define FHQTREAP_H_INCLUDED

 //author Eterna
 #define Hello The_Cruel_World!
 #pragma GCC optimize(2)
 #include<iostream>
 #include<algorithm>
 #include<cstdio>
 #include<string>
 #include<cstring>
 #include<vector>
 #include<map>
 #include<set>
 #include<queue>
 #include<stack>
 #include<utility>
 #include<cmath>
 #include<climits>
 #include<deque>
 #include<functional>
 #include<complex>
 #include<numeric>
 #define max(x,y) ((x)>(y)?(x):(y))
 #define min(x,y) ((x)<(y)?(x):(y))
 #define Pi acos(-1.0)
 #define ABS(x) ((x) >= 0 ? (x) : (-(x)))
 #define pb(x) push_back(x)
 #define lowbit(x) (x & -x)
 #define FRIN freopen("C:\\Users\\Administrator.MACHENI-KA32LTP\\Desktop\\in.txt", "r", stdin)
 #define FROUT freopen("C:\\Users\\Administrator.MACHENI-KA32LTP\\Desktop\\out.txt", "w", stdout)
 #define FAST ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
 using namespace std;
 typedef long long ll;
 typedef unsigned long long ull;
 typedef pair<int, int> pii;
 const int maxn = 1e5;
 const int INF = 0x7fffffff;
 const int mod = 1e9 + ;
 const double eps = 1e-;
 inline int read_int() {
     char c;
     int ret = , sgn = ;
     do { c = getchar(); } while ((c < '' || c > '') && c != '-');
     if (c == '-') sgn = -; else ret = c - '';
     while ((c = getchar()) >= '' && c <= '') ret = ret *  + (c - '');
     return sgn * ret;
 }
 inline ll read_ll() {
     char c;
     ll ret = , sgn = ;
     do { c = getchar(); } while ((c < '' || c > '') && c != '-');
     if (c == '-') sgn = -; else ret = c - '';
     while ((c = getchar()) >= '' && c <= '') ret = ret *  + (c - '');
     return sgn * ret;
 }
 struct node {
     int value, key, Size, child[];
 }arr[maxn + ];
 int tot;
 inline void Push_Up(int index) {
     arr[index].Size = arr[arr[index].child[]].Size + arr[arr[index].child[]].Size + ;
 }
 void Split_By_Size(int root, int& a, int& b, int k) {
     if (!root) {
         a = b = ;
         return;
     }
     if (arr[arr[root].child[]].Size < k) a = root, Split_By_Size(arr[root].child[], arr[a].child[], b, k - arr[arr[root].child[]].Size - );
     else b = root, Split_By_Size(arr[root].child[], a, arr[b].child[], k);
     Push_Up(root);
 }
 void Split_By_Value(int root, int& a, int& b, int value) {
     if (!root) {
         a = b = ;
         return;
     }
     if (arr[root].value <= value)a = root, Split_By_Value(arr[root].child[], arr[a].child[], b, value);
     else b = root, Split_By_Value(arr[root].child[], a, arr[b].child[], value);
     Push_Up(root);
 }
 void Merge(int& root, int a, int b) {
     if (!a || !b) {
         root = a + b;
         return;
     }
     if (arr[a].key < arr[b].key)root = a, Merge(arr[root].child[], arr[a].child[], b);
     else root = b, Merge(arr[root].child[], a, arr[b].child[]);
     Push_Up(root);
 }
 inline void Insert(int& root, int value) {
     int x = , y = , z = ++tot;
     arr[z].value = value, arr[z].key = rand(), arr[z].Size = ;
     Split_By_Value(root, x, y, value);
     Merge(x, x, z);
     Merge(root, x, y);
 }
 inline void Erase(int& root, int value) {
     int x = , y = , z = ;
     Split_By_Value(root, x, y, value);
     Split_By_Value(x, x, z, value - );
     Merge(z, arr[z].child[], arr[z].child[]);
     Merge(x, x, z);
     Merge(root, x, y);
 }
 int Kth_number(int root, int k) {
     while (arr[arr[root].child[]].Size +  != k) {
         if (arr[arr[root].child[]].Size >= k)root = arr[root].child[];
         else k -= (arr[arr[root].child[]].Size + ), root = arr[root].child[];
     }
     return arr[root].value;
 }
 int Get_Rank(int& root, int value) {
     int x = , y = ;
     Split_By_Value(root, x, y, value - );
     int res = arr[x].Size + ;
     Merge(root, x, y);
     return res;
 }
 int Predecessor(int& root, int value) {
     int x = , y = ;
     Split_By_Value(root, x, y, value - );
     int res = Kth_number(x, arr[x].Size);
     Merge(root, x, y);
     return res;
 }
 int Successor(int& root, int value) {
     int x = , y = ;
     Split_By_Value(root, x, y, value);
     int res = Kth_number(y, );
     Merge(root, x, y);
     return res;
 }
 int n, op, u, root;
 int main()
 {
     srand();
     scanf("%d", &n);
     while (n--) {
         scanf("%d %d", &op, &u);
         if (op == )Insert(root, u);
         if (op == )Erase(root, u);
         if (op == )printf("%d\n", Get_Rank(root, u));
         if (op == )printf("%d\n", Kth_number(root, u));
         if (op == )printf("%d\n", Predecessor(root, u));
         if (op == )printf("%d\n", Successor(root, u));
     }
     return ;
 }

 #endif // FHQTREAP_H_INCLUDED