splay tree

codes/splay-tree-rr-sir.cpp

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+//Splay Tree
+//used here by rr sir, I have no idea how to use it or what it's used in mostly, [RR Sir ABC F Submission](https://atcoder.jp/contests/abc350/submissions/52600529)
+
+
+#include <ext/pb_ds/assoc_container.hpp> 
+#include <ext/pb_ds/tree_policy.hpp>
+
+namespace allocator {
+
+// Array allocator.
+template <class T, int MAXSIZE>
+struct array {
+  T v[MAXSIZE], *top;
+  array() : top(v) {}
+  T *alloc(const T &val = T()) { return &(*top++ = val); }
+  void dealloc(T *p) {}
+};
+
+// Stack-based array allocator.
+template <class T, int MAXSIZE>
+struct stack {
+  T v[MAXSIZE];
+  T *spot[MAXSIZE], **top;
+  stack() {
+    for (int i = 0; i < MAXSIZE; ++i) spot[i] = v + i;
+    top = spot + MAXSIZE;
+  }
+  T *alloc(const T &val = T()) { return &(**--top = val); }
+  void dealloc(T *p) { *top++ = p; }
+};
+
+}  // namespace allocator
+
+namespace splay {
+
+// Abstract node struct.
+template <class T>
+struct node {
+  T *f, *c[2];
+  int size;
+  node() {
+    f = c[0] = c[1] = nullptr;
+    size = 1;
+  }
+  void push_down() {}
+  void update() {
+    size = 1;
+    for (int t = 0; t < 2; ++t)
+      if (c[t]) size += c[t]->size;
+  }
+};
+
+// Abstract reversible node struct.
+template <class T>
+struct reversible_node : node<T> {
+  int r;
+  reversible_node() : node<T>() { r = 0; }
+  void push_down() {
+    node<T>::push_down();
+    if (r) {
+      for (int t = 0; t < 2; ++t)
+        if (node<T>::c[t]) node<T>::c[t]->reverse();
+      r = 0;
+    }
+  }
+  void update() { node<T>::update(); }
+  // Reverse the range of this node.
+  void reverse() {
+    std::swap(node<T>::c[0], node<T>::c[1]);
+    r = r ^ 1;
+  }
+};
+
+template <class T, int MAXSIZE = 500000,
+          class alloc = allocator::array<T, MAXSIZE + 2>>
+struct tree {
+  alloc pool;
+  T *root;
+  // Get a new node from the pool.
+  T *new_node(const T &val = T()) { return pool.alloc(val); }
+  tree() {
+    root = new_node(), root->c[1] = new_node(), root->size = 2;
+    root->c[1]->f = root;
+  }
+  // Helper function to rotate node.
+  void rotate(T *n) {
+    int v = n->f->c[0] == n;
+    T *p = n->f, *m = n->c[v];
+    if (p->f) p->f->c[p->f->c[1] == p] = n;
+    n->f = p->f, n->c[v] = p;
+    p->f = n, p->c[v ^ 1] = m;
+    if (m) m->f = p;
+    p->update(), n->update();
+  }
+  // Splay n so that it is under s (or to root if s is null).
+  void splay(T *n, T *s = nullptr) {
+    while (n->f != s) {
+      T *m = n->f, *l = m->f;
+      if (l == s)
+        rotate(n);
+      else if ((l->c[0] == m) == (m->c[0] == n))
+        rotate(m), rotate(n);
+      else
+        rotate(n), rotate(n);
+    }
+    if (!s) root = n;
+  }
+  // Get the size of the tree.
+  int size() { return root->size - 2; }
+  // Helper function to walk down the tree.
+  int walk(T *n, int &v, int &pos) {
+    n->push_down();
+    int s = n->c[0] ? n->c[0]->size : 0;
+    (v = s < pos) && (pos -= s + 1);
+    return s;
+  }
+  // Insert node n to position pos.
+  void insert(T *n, int pos) {
+    T *c = root;
+    int v;
+    ++pos;
+    while (walk(c, v, pos), c->c[v] && (c = c->c[v]))
+      ;
+    c->c[v] = n, n->f = c, splay(n);
+  }
+  // Find the node at position pos. If sp is true, splay it.
+  T *find(int pos, int sp = true) {
+    T *c = root;
+    int v;
+    ++pos;
+    while ((pos < walk(c, v, pos) || v) && (c = c->c[v]))
+      ;
+    if (sp) splay(c);
+    return c;
+  }
+  // Find the range [posl, posr) on the splay tree.
+  T *find_range(int posl, int posr) {
+    T *r = find(posr), *l = find(posl - 1, false);
+    splay(l, r);
+    if (l->c[1]) l->c[1]->push_down();
+    return l->c[1];
+  }
+  // Insert nn of size nn_size to position pos.
+  void insert_range(T **nn, int nn_size, int pos) {
+    T *r = find(pos), *l = find(pos - 1, false), *c = l;
+    splay(l, r);
+    for (int i = 0; i < nn_size; ++i) c->c[1] = nn[i], nn[i]->f = c, c = nn[i];
+    for (int i = nn_size - 1; i >= 0; --i) nn[i]->update();
+    l->update(), r->update(), splay(nn[nn_size - 1]);
+  }
+  // Helper function to dealloc a subtree.
+  void dealloc(T *n) {
+    if (!n) return;
+    dealloc(n->c[0]);
+    dealloc(n->c[1]);
+    pool.dealloc(n);
+  }
+  // Remove from position [posl, posr).
+  void erase_range(int posl, int posr) {
+    T *n = find_range(posl, posr);
+    n->f->c[1] = nullptr, n->f->update(), n->f->f->update(), n->f = nullptr;
+    dealloc(n);
+  }
+};
+
+}  // namespace splay
+
+const int MAXSIZE = 500005;
+
+struct node: splay::reversible_node<node> {
+  long long val, val_min, label_add;
+  node(long long v = 0) : splay::reversible_node<node>(), val(v) { val_min = label_add = 0; }
+  // Add v to the subtree.
+  void add(long long v) {
+    val += v;
+    val_min += v;
+    label_add += v;
+  }
+  void push_down() {
+    splay::reversible_node<node>::push_down();
+    for (int t = 0; t < 2; ++t) if (c[t]) c[t]->add(label_add);
+    label_add = 0;
+  } 
+  void update() {
+    splay::reversible_node<node>::update();
+    val_min = val;
+    for (int t = 0; t < 2; ++t) if (c[t]) val_min = std::min(val_min, c[t]->val_min);
+  }
+};
+
+splay::tree<node, MAXSIZE, allocator::stack<node, MAXSIZE + 2>> t;