1. 插入元素。
2. 删除元素。
3. 查询元素的排名。
4. 查询第k小的元素。
5. 查询元素前趋。
6. 查询元素后继。

BBST裸题。

# 代码

#include <cstdio>
#include <iostream>
#define ll long long
using namespace std;
#ifdef D
const int maxn = 100;
#else
const int maxn = 100005;
#endif
int ch[maxn][2], fa[maxn], size[maxn], data[maxn], cnt[maxn];
int rt, n, m;
ll sz = 0;
int x = 0, f = 1;
char ch = getchar();
while (ch < '0' || ch > '9') {
if (ch == '-')
f = -1;
ch = getchar();
}
while (ch >= '0' && ch <= '9') {
x = x * 10 + ch - '0';
ch = getchar();
}
return x * f;
}
inline void update(int x) {
size[x] = size[ch[x][0]] + size[ch[x][1]] + cnt[x];
}
inline void zig(int x) {
int y = fa[x], z = fa[y], l = (ch[y][1] == x), r = l ^ 1;
fa[ch[y][l] = ch[x][r]] = y;
fa[ch[x][r] = y] = x;
fa[x] = z;
if (z)
ch[z][ch[z][1] == y] = x;
update(y);
}
inline void splay(int x, int aim = 0) { //调整x成为aim的儿子
for (int y; (y = fa[x]) != aim; zig(x)) {
if (fa[y] != aim)
zig((ch[y][0] == x) == (ch[fa[y]][0] == y) ? y : x);
}
if (aim == 0)
rt = x;
update(x);
}
inline void insert(int v) {
int x = rt;
if (rt == 0) {
rt = x = ++sz;
data[x] = v;
fa[x] = ch[x][0] = ch[x][1] = 0;
size[x] = cnt[x] = 1;
return;
}
while (x) {
size[x]++;
if (v == data[x]) {
cnt[x]++;
return;
}
int &y = ch[x][v >= data[x]];
if (y == 0) {
y = ++sz;
data[y] = v;
fa[y] = x;
ch[y][0] = ch[y][1] = 0;
size[y] = cnt[y] = 1;
x = y;
break;
}
x = y;
}
splay(x);
}
int rank(int v) {
int ret = 0, ans, x = rt;
while (x) {
if (v > data[x]) {
ret += size[ch[x][0]] + cnt[x];
x = ch[x][1];
} else {
if (v == data[x]) {
return ret + size[ch[x][0]] + 1;
}
x = ch[x][0];
}
}
}
int kth(int v) {
int x = rt;
while (x) {
if (v >= size[ch[x][0]] + 1 && v <= size[ch[x][0]] + cnt[x])
return data[x];
if (v > size[ch[x][0]] + cnt[x]) {
v -= size[ch[x][0]] + cnt[x];
x = ch[x][1];
} else
x = ch[x][0];
}
}
int pre(int v) {
int ans;
for (int y = rt; y;)
if (data[y] < v)
ans = data[y], y = ch[y][1];
else
y = ch[y][0];
return ans;
}
int succ(int v) {
int ans;
for (int y = rt; y;)
if (data[y] <= v)
y = ch[y][1];
else
ans = data[y], y = ch[y][0];
return ans;
}
inline void del(int v) {
int x = rt;
while (x) {
size[x]--;
if (data[x] == v) {
cnt[x]--;
break;
}
int &y = ch[x][v >= data[x]];
x = y;
}
if (cnt[x] != 0)
return;
splay(x);
if (ch[x][0] == 0) {
rt = ch[x][1];
fa[rt] = 0;
return;
}
if (ch[x][1] == 0) {
rt = ch[x][0];
fa[rt] = 0;
return;
}
x = ch[rt][0];
while (ch[x][1])
x = ch[x][1];
splay(x, rt);
ch[x][1] = ch[rt][1];
fa[ch[x][1]] = x;
size[x] = size[rt] - 1;
fa[x] = 0;
rt = x;
}
int main() {
#ifdef DEBUG
freopen("input", "r", stdin);
#endif
scanf("%d", &n);
rt = sz = 0;
while (n--) {
if (opt == 1) {
insert(x); // O(log n)
} else if (opt == 2) {
del(x); // O(log n)
} else if (opt == 3) {
printf("%d\n", rank(k));
} else if (opt == 4) {