1 files changed, 79 insertions, 0 deletions
diff --git a/content/datastructures/treap.cpp b/content/datastructures/treap.cpp
new file mode 100644
index 0000000..c96e36a
--- /dev/null
+++ b/content/datastructures/treap.cpp
@@ -0,0 +1,79 @@
+struct node {
+	int key, prio, left, right, size;
+	node(int key, int prio) : key(key), prio(prio), left(-1),
+	                          right(-1), size(1) {};
+};
+
+vector<node> treap;
+
+int getSize(int root) {
+	return root < 0 ? 0 : treap[root].size;
+}
+
+void update(int root) {
+	if (root < 0) return;
+	treap[root].size = 1 + getSize(treap[root].left)
+	                     + getSize(treap[root].right);
+}
+
+pair<int, int> split(int root, int minKeyRight) {
+	if (root < 0) return {-1, -1};
+	if (treap[root].key >= minKeyRight) {
+		auto leftSplit = split(treap[root].left, minKeyRight);
+		treap[root].left = leftSplit.second;
+		update(root);
+		leftSplit.second = root;
+		return leftSplit;
+	} else {
+		auto rightSplit = split(treap[root].right, minKeyRight);
+		treap[root].right = rightSplit.first;
+		update(root);
+		rightSplit.first = root;
+		return rightSplit;
+}}
+
+int merge (int left, int right) {
+	if (left < 0) return right;
+	if (right < 0) return left;
+	if (treap[left].prio < treap[right].prio) { //min priority heap
+		treap[left].right = merge(treap[left].right, right);
+		update(left);
+		return left;
+	} else {
+		treap[right].left = merge(left, treap[right].left);
+		update(right);
+		return right;
+}}
+
+//insert values with high priority first
+int insert(int root, int key, int prio) {
+	int next = sz(treap);
+	treap.emplace_back(key, prio);
+	auto t = split(root, key);
+	//returns new root
+	return merge(merge(t.first, next), t.second);
+}
+
+int remove(int root, int key) {
+	if (root < 0) return -1;
+	if (key < treap[root].key) {
+		treap[root].left = remove(treap[root].left, key);
+		update(root);
+		return root;
+	} else if (key > treap[root].key) {
+		treap[root].right = remove(treap[root].right, key);
+		update(root);
+		return root;
+	} else { //check prio?
+		return merge(treap[root].left, treap[root].right);
+}}
+
+int kth(int root, int k) {
+	if (root < 0) return -1;
+	int leftSize = getSize(treap[root].left);
+	if (k < leftSize) return kth(treap[root].left, k);
+	else if (k > leftSize) {
+		return kth(treap[root].right, k - 1 - leftSize);
+	}
+	return root;
+}