Adding treap code and changes on LCA code.

1 files changed, 39 insertions, 0 deletions

diff --git a/datastructures/treap.cpp b/datastructures/treap.cpp
new file mode 100644
index 0000000..7c4ce7f
--- /dev/null
+++ b/datastructures/treap.cpp
@@ -0,0 +1,39 @@
+struct item {
+  int key, prior;
+  item *l, *r;
+  item() { }
+  item (int key, int prior) : key(key), prior(prior), l(NULL), r(NULL) { }
+};
+
+void split (item *t, int key, item *l, item *r) {
+  if (!t) l = r = NULL;
+  else if (key < t->key) split(t->l, key, l, t->l), r = t;
+  else split(t->r, key, t->r, r), l = t;
+}
+
+void insert (item *t, item *it) {
+  if (!t) t = it;
+  else if (it->prior > t->prior) split(t, it->key, it->l, it->r), t = it;
+  else insert(it->key < t->key ? t->l : t->r, it);
+}
+
+void merge (item *t, item *l, item *r) {
+  if (!l || !r) t = l ? l : r;
+  else if (l->prior > r->prior) merge(l->r, l->r, r), t = l;
+  else merge(r->l, l, r->l), t = r;
+}
+
+void erase (item *t, int key) {
+  if (t->key == key) merge (t, t->l, t->r);
+  else erase(key < t->key ? t->l : t->r, key);
+}
+
+item *unite (item *l, item *r) {
+  if (!l || !r)  return l ? l : r;
+  if (l->prior < r->prior) swap(l, r);
+  item * lt, rt;
+  split(r, l->key, lt, rt);
+  l->l = unite(l->l, lt);
+  l->r = unite(l->r, rt);
+  return l;
+}