平衡树（fhq无旋treap）

splay

普通平衡树

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;

int read(void) {
	int x = 0; bool f = 0;
	char c = getchar();
	for (;!isdigit(c);c=getchar()) if (c=='-') f=1;
	for (;isdigit(c);c=getchar()) x=(x<<3)+(x<<1)+(c^48);
	if (f) return -x;
	return x;
}

const int N = 100005;
const int INF = 0x7fffffff;
int v[N], f[N], son[N][2];
int cnt[N], siz[N], tot;
int val[N], n, sz, root;

inline void update(int x) {
	siz[x] = siz[son[x][0]] + siz[son[x][1]] + cnt[x];
}

inline void rotate(int x) {
	int y = f[x], z = f[y];;
	int k = son[f[x]][1] == x, w = son[x][k^1];
	son[y][k] = w, f[w] = y;
	son[z][son[z][1] == y] = x, f[x] = z;
	son[x][k^1] = y, f[y] = x;
	update(y), update(x);
}

inline void splay(int x,int t) {
	while (f[x] != t) {
		int y = f[x], z = f[y];
		if (z != t) {
			if ((son[y][1] == x) ^ (son[z][1] == y))
				rotate(x);
			else rotate(y);
		}
		rotate(x);
	}
	if (t == 0) root = x;
}

inline void insert(int x) {
	int p = root, pre = 0;
	while (p && val[p] != x)
		pre = p, p = son[p][val[p] < x];
	if (p) cnt[p]++;
	else {
		p = ++sz; cnt[p] = siz[p] = 1;
		if (pre) son[pre][val[pre] < x] = p;
		son[p][0] = son[p][1] = 0;
		f[p] = pre, val[p] = x;
	}
	splay(p, 0);
}

inline void find(int x) {
	int p = root;
	while (son[p][val[p] < x] && val[p] != x)
		p = son[p][val[p] < x];
	splay(p, 0);
}

inline int get_rk(int x) {
	find(x);
	return siz[son[root][0]];
}

inline int kth(int x) {
	int p = root; x++;
	while (true) {
		if (son[p][0] && x <= siz[son[p][0]]) p = son[p][0];
		else if (x > siz[son[p][0]] + cnt[p])
			x -= siz[son[p][0]] + cnt[p], p = son[p][1];
		else return val[p];
	}
}

inline int get_pre(int x) {
	find(x);
	if (val[root] < x) return root;
	int p = son[root][0];
	while (son[p][1]) p = son[p][1];
	return p;
}

inline int get_nxt(int x) {
	find(x);
	if (val[root] > x) return root;
	int p = son[root][1];
	while (son[p][0]) p = son[p][0];
	return p;
}

inline void del(int x) {
	int pre = get_pre(x), nxt = get_nxt(x);
	splay(pre, 0), splay(nxt, root);
	int p = son[nxt][0];
	if (cnt[p] > 1) cnt[p]--, splay(p, 0);
	else son[nxt][0] = 0, update(nxt), update(root);
}

int main() {
	int opt, x; n = read();
	insert(INF), insert(-INF);
	for (int i = 1;i <= n; i++) {
		opt = read(), x = read();
		if (opt == 1) insert(x);
		else if (opt == 2) del(x);
		else if (opt == 3) printf ("%d\n", get_rk(x));
		else if (opt == 4) printf ("%d\n", kth(x));
		else if (opt == 5) printf ("%d\n", val[get_pre(x)]);
		else printf ("%d\n", val[get_nxt(x)]);
	}
	return 0;
}

文艺平衡树

#include<iostream>
#include<cstring>
#include<cstdio>
using namespace std;
const int N = 200050;
const int INF = 0x7fffffff;
int read(void) {
	int x = 0; bool f = 0;
	char c = getchar();
	for (;!isdigit(c);c=getchar()) if (c=='-') f=1;
	for (;isdigit(c);c=getchar()) x=(x<<3)+(x<<1)+(c^48);
	return f ? -x : x;
}

int val[N], son[N][2];
int tag[N], f[N], n, sz;
int siz[N], rt;

void update(int x) {
	siz[x] = siz[son[x][1]] + siz[son[x][0]] + 1;
}

void spread(int x) {
	if (!tag[x]) return;
	swap(son[x][0], son[x][1]);
	if (son[x][0]) tag[son[x][0]] ^= 1;
	if (son[x][1]) tag[son[x][1]] ^= 1;
	tag[x] = 0;
}

int kth(int k) {
	int x = rt;
	while (true) {
		spread(x);
		if (siz[son[x][0]] >= k) x = son[x][0];
		else if (siz[son[x][0]] + 1 == k) return x;
		else k -= siz[son[x][0]] + 1, x = son[x][1];
	}
}

void rotate(int x) {
	int y = f[x], z = f[y];
	int k = son[y][1] == x, w = son[x][k^1];
	son[y][k] = w, f[w] = y;
	f[y] = x, son[x][k^1] = y;
	son[z][son[z][1]==y] = x, f[x] = z;
	update(y), update(x);
}

void splay(int x,int t) {
	while (f[x] != t) {
		int y = f[x], z = f[y];
		if (z != t) {
			if ((son[z][1]==y)^(son[y][1]==x))
				rotate(x);
			else rotate(y);
		}
		rotate(x);
	}
	if (t == 0) rt = x;
}

void insert(int x) {
	int p = rt, pre = 0;
	while (p)
		pre = p, p = son[p][val[p] < x];
	p = ++sz;
	if (pre) son[pre][val[pre]<x] = p;
	siz[p] = 1, son[p][0] = son[p][1] = 0;
	f[p] = pre, val[p] = x;
	splay(p, 0);
}

void rec(int x) {
	spread(x);
	if (son[x][0]) rec(son[x][0]);
	if (val[x] > 1 && val[x] < n + 2)
	printf ("%d ", val[x]-1);
	if (son[x][1]) rec(son[x][1]);
}

inline void work(int l,int r) {
	l = kth(l), r = kth(r+2);
	splay(l, 0); splay(r, rt);
	tag[son[son[rt][1]][0]] ^= 1;
}

int m, l, r;
int main() {
	n = read(), m = read();
	for (int i = 1;i <= n + 2; i++)
	insert(i);
	while (m--) {
		l = read(), r = read();
		work(l, r);
	}
	rec(rt);
	cout << endl;
	return 0;
}

fhq板子(代码正确且风格易懂）

洛谷P3369

#include<iostream>
#include<cstring>
#include<cstdio>
#include<ctime>
#include<cstdlib>
using namespace std;
const int N = 105000;
int val[N], son[N][2];
int rnd[N], tot, n;
int siz[N], root, a, p, x, y, z;
inline void update(int x) {
	siz[x] = siz[son[x][1]] + siz[son[x][0]] + 1;
}
inline int build(int x) {
	siz[++tot] = 1, rnd[tot] = rand();
	val[tot] = x; return tot;
}
int merge(int x,int y) {
	if (!x || !y) return x + y;
	if (rnd[x] < rnd[y]) {
		son[x][1] = merge(son[x][1], y);
		update(x); return x;
	}
	son[y][0] = merge(x, son[y][0]);
	update(y); return y;
}
void split(int now,int k,int &x,int &y) {
	if (!now) x = y = 0;
	else {
		if (val[now] <= k) x = now, split(son[x][1], k, son[x][1], y);
		else y = now, split(son[y][0], k, x, son[y][0]);
		update(now);
	}
}

inline int kth(int now, int k) {
	while (1) {
		if (k <= siz[son[now][0]]) now = son[now][0];
		else if (k == siz[son[now][0]] + 1) return now;
		else k -= siz[son[now][0]] + 1, now = son[now][1];
	}
}
template <typename T>
void read(T &x) {
	x = 0; int f = 1;char c = getchar();
	while (!isdigit(c)) { if (c == '-') f = -1; c = getchar();}
	while (isdigit(c)) { x = (x << 3)+(x << 1) + c-'0'; c = getchar();}
	x *= f;
}
int main() {
	srand(time(0));
	read(n);
	for (int i = 1;i <= n; i++) {
		read(p), read(a);
		if (p == 1) {
			split(root, a, x, y);
			root = merge(merge(x, build(a)), y);
		}
		else if (p == 2) {
			split(root, a, x, y);
			split(x, a-1, x, z);
			z = merge(son[z][0], son[z][1]);
			root = merge(merge(x, z), y);
		}
		else if (p == 3) {
			split(root, a-1, x, y);
			printf ("%d\n", siz[x] + 1);
			root = merge(x, y);
		}
		else if (p == 4) printf ("%d\n", val[kth(root, a)]);
		else if (p == 5) {
			split(root, a-1, x, y);
			printf ("%d\n", val[kth(x, siz[x])]);
			root = merge(x, y);
		}
		else {
			split(root, a, x, y);
			printf ("%d\n", val[kth(y, 1)]);
			root = merge(x, y);
		}
	}
	return 0;
}

洛谷P3391

#include<iostream>
#include<cstring>
#include<cstdio>
#include<cstdlib>
#include<ctime>
using namespace std;
const int N = 100050;
int rnd[N], siz[N];
int cnt, n, l, r;
int tag[N], son[N][2];
int val[N], root, x, y, z;
inline int build(int x) {
	siz[++cnt] = 1, val[cnt] = x;
	rnd[cnt] = rand(); return cnt;
}
inline void update(int x) {
	siz[x] = siz[son[x][1]] + siz[son[x][0]] + 1;
}
void spread(int x) {
	if (tag[x]) {
		swap(son[x][0], son[x][1]);
		if (son[x][0]) tag[son[x][0]] ^= 1;
		if (son[x][1]) tag[son[x][1]] ^= 1;
		tag[x] = 0;
	}
}
void split(int now,int k,int &x,int &y) {
	if (!now) x = y = 0;
	else {
		spread(now);
		if (siz[son[now][0]] < k) x = now, split(son[x][1], k - siz[son[now][0]] - 1, son[x][1], y);
		else y = now, split(son[y][0], k, x, son[y][0]);
		update(now);
	}
}
int merge(int x,int y) {
	if(!x || !y) return x + y;
	if (rnd[x] < rnd[y]) {
		spread(x);
		son[x][1] = merge(son[x][1], y);
		update(x); return x;
	}
	spread(y);
	son[y][0] = merge(x, son[y][0]);
	update(y); return y;
}
template <typename T>
void read(T &x) {
	x = 0; int f = 1;char c = getchar();
	while (!isdigit(c)) { if (c == '-') f = -1; c = getchar();}
	while (isdigit(c)) { x = (x << 3)+(x << 1) + c-'0'; c = getchar();}
	x *= f;
}
int m;
void res(int x) {
	if (!x) return;
	spread(x);
	res(son[x][0]);
	printf ("%d ", val[x]);
	res(son[x][1]);
}
int main() {
	read(n), read(m);
	for (int i = 1;i <= n; i++) root = merge(root, build(i));
	while (m--) {
		read(l), read(r);
		split(root, l - 1, x, y);
		split(y, r - l+ 1, y, z);
		tag[y] ^= 1;
		root = merge(merge(x, y), z);
	}
	res(root);
	return 0;
}

可持久化平衡树

p3835

#include<iostream>
#include<cstdio>
#include<ctime>
#include<cstdlib>
#include<cstring>
using namespace std;
const int N = 500500 * 50;
const int INF = 2147483647;
int T[N], val[N], rnd[N];
int siz[N], son[N][2];
int cnt; 

template <typename T>
void read(T &x) {
	x = 0; int f = 1;char c = getchar();
	while (!isdigit(c)) { if (c == '-') f = -1; c = getchar();}
	while (isdigit(c)) { x = (x << 3)+(x << 1) + c-'0'; c = getchar();}
	x *= f;
}

inline void update(int x) {
	siz[x] = siz[son[x][0]] + siz[son[x][1]] + 1;
}

inline void cpy(int x,int y) {
	siz[x] = siz[y], son[x][1] = son[y][1];
	son[x][0] = son[y][0];
	val[x] = val[y], rnd[x] = rnd[y];
}
inline int build(int x) {
	val[++cnt] = x, siz[cnt] = 1;
	rnd[cnt] = rand(); return cnt;
}

void split(int now,int k,int &x,int &y) {
	if (!now) x = y = 0;
	else {
		if (val[now] <= k) {
			x = ++cnt, cpy(x, now), split(son[x][1], k, son[x][1], y);
			update(x);
		}
		else {
			y = ++cnt, cpy(y, now), split(son[y][0], k, x, son[y][0]);
			update(y);
		}
	}
}

int merge(int x,int y) {
	if (!x || !y) return x + y;
	if (rnd[x] < rnd[y]) {
		int p = ++cnt; cpy(p, x);
		son[p][1] = merge(son[p][1], y);
		update(p); return p;
	}
	int p = ++cnt; cpy(p, y);
	son[p][0] = merge(x, son[p][0]);
	update(p); return p;
} 

int kth(int now,int x) {
	while (1) {
		if (siz[son[now][0]] >= x) now = son[now][0];
		else if (siz[son[now][0]] + 1 == x) return now;
		else x -= siz[son[now][0]] + 1, now = son[now][1];
	}
}

int n, x, y, z;
int op, P, a;
int main() {
	srand(20040202);
	read(n);
	for (int i = 1;i <= n; i++) {
		read(P), read(op), read(a);
		T[i] = T[P];
		if (op == 1) {
			split(T[i], a, x, y);
			T[i] = merge(merge(x, build(a)), y);
		}
		else if (op == 2) {
			split(T[i], a, x, z);
			split(x, a-1, x, y);
			y = merge(son[y][0], son[y][1]);
			T[i] = merge(merge(x, y), z);
		}
		else if (op == 3) {
			split(T[i], a-1, x, y);
			printf ("%d\n", siz[x] + 1);
			T[i] = merge(x, y);
		}
		else if (op == 4) printf ("%d\n", val[kth(T[i], a)]);
		else if (op == 5) {
			split(T[i], a-1, x, y);
			if (siz[x] == 0) printf ("%d\n", -INF);
			else printf ("%d\n", val[kth(x, siz[x])]);
			T[i] = merge(x, y);
		}
		else if (op == 6) {
			split(T[i], a, x, y);
			if (siz[y] == 0) printf ("%d\n", INF);
			else printf ("%d\n", val[kth(y, 1)]);
			T[i] = merge(x, y);
		}
	}
	return 0;
}