如題，這是一個模板。。。

  1 #include <algorithm>
  2 #include <iostream>
  3 #include <cstring>
  4 #include <cstdio>
  5 #include <cctype>
  6 
  7 inline void read(int & x)
  8 {
  9     x = 0;
 10     int k = 1;
 11     char c = getchar();
 12     while (!isdigit(c))
 
 13         if (c == '-') c = getchar(), k = -1;
 14         else c = getchar();
 15     while (isdigit(c))
 16         x = (x << 1) + (x << 3) + (c ^ 48),
 17         c = getchar();
 18     x *= k;
 19 }
 20 
 21 const int MAXN = 101100;
 22 int n, tot = 0, rt = 0;
 23 int cnt[MAXN], siz[MAXN], val[MAXN], rnd[MAXN];
 
 24 int son[MAXN][2];
 25 
 26 inline int Rand(void)
 27 {
 28     static int seed = 1024;
 29     return seed = (int)seed * 482711LL % 2147483647;
 30 }
 31 
 32 inline void Pushup(int u)
 33 {
 34     siz[u] = siz[son[u][0]] + siz[son[u][1]] + cnt[u];
 35 }
 36 
 37 inline void Rotate(int
 
 &u, int ch)
 38 {
 39     int b = son[u][ch ^ 1];
 40     son[u][ch ^ 1] = son[b][ch];
 41     son[b][ch] = u;
 42     Pushup(u), Pushup(u = b);
 43 }
 44 
 45 inline void Insert(int &u, int x)
 46 {
 47     if (!u)
 48     {
 49         u = ++tot;
 50         cnt[u] = siz[u] = 1;
 51         val[u] = x, rnd[u] = Rand();
 52         son[u][0] = son[u][1] = 0;
 53         return;
 54     }
 55     ++siz[u];
 56     if (val[u] == x) { ++cnt[u]; return; }
 57     int ch = val[u] < x; Insert(son[u][ch], x);
 58     if (rnd[u] > rnd[son[u][ch]]) Rotate(u, ch ^ 1);
 59 }
 60 
 61 inline void Delete(int &u, int x)
 62 {
 63     if (!u) return;
 64     if (val[u] == x)
 65     {
 66         if (cnt[u] > 1) { --cnt[u], --siz[u]; return; }
 67         int ch = rnd[son[u][0]] < rnd[son[u][1]];
 68         if (!son[u][0] || !son[u][1]) u = son[u][0] + son[u][1];
 69         else Rotate(u, ch), Delete(u, x);
 70     }
 71     else --siz[u], Delete(son[u][val[u] < x], x);
 72 }
 73 
 74 inline int Getrank(int u, int x)
 75 {
 76     if (!u) return 0;
 77     if (val[u] == x) return siz[son[u][0]] + 1;
 78     if (val[u] > x) return Getrank(son[u][0], x);
 79     else return Getrank(son[u][1], x) + siz[son[u][0]] + cnt[u];
 80 }
 81 
 82 inline int Getkth(int k)
 83 {
 84     int u = rt;
 85     while (true)
 86         if (k <= siz[son[u][0]]) u = son[u][0];
 87         else if (k > siz[son[u][0]] + cnt[u]) 
 88             k -= siz[son[u][0]] + cnt[u], u = son[u][1];
 89         else return val[u];
 90 }
 91 
 92 inline int Pre(int x)
 93 {
 94     int u = rt, pre = -2147483600;
 95     while (u)
 96         if (x > val[u]) pre = val[u], u = son[u][1];
 97         else u = son[u][0];
 98     return pre;
 99 }
100 
101 inline int Suf(int x)
102 {
103     int u = rt, suf = 2147483600;
104     while (u)
105         if (x < val[u]) suf = val[u], u = son[u][0];
106         else u = son[u][1];
107     return suf;
108 }
109 
110 int opt, x;
111 
112 signed main()
113 {
114     read(n);
115     for (int i = 1; i <= n; ++i)
116     {
117         read(opt), read(x);
118         if (opt == 1) Insert(rt, x);
119         if (opt == 2) Delete(rt, x);
120         if (opt == 3) printf("%d\n", Getrank(rt, x));
121         if (opt == 4) printf("%d\n", Getkth(x));
122         if (opt == 5) printf("%d\n", Pre(x));
123         if (opt == 6) printf("%d\n", Suf(x));
124     }
125     return 0;
126 }