From 8fe0795dd0e6cac1ad90874b0bfcc6d301b7d14f Mon Sep 17 00:00:00 2001
From: Chris Beall <chrisbeall@gmail.com>
Date: Thu, 4 Feb 2010 21:02:05 +0000
Subject: [PATCH] BTree moved into gtsam

---
 cpp/BTree.h | 117 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 117 insertions(+)
 create mode 100644 cpp/BTree.h

diff --git a/cpp/BTree.h b/cpp/BTree.h
new file mode 100644
index 000000000..206d0bc89
--- /dev/null
+++ b/cpp/BTree.h
@@ -0,0 +1,117 @@
+/*
+ *  Created on: Feb 3, 2010
+ *      Author: cbeall3
+ */
+
+#include <boost/shared_ptr.hpp>
+#include <CppUnitLite/TestHarness.h>
+#include "Key.h"
+
+//    type 'a t =
+//        Empty
+//      | Node of 'a t * key * 'a * 'a t * int
+
+namespace gtsam{
+
+template <class Key, class Value>
+struct Node {
+	typedef boost::shared_ptr<Node> Tree;
+	Tree left_, right_;
+	Key key_;
+	Value value_;
+	size_t height_;
+	/**
+	 * leaf node with height 1
+	 */
+	Node(const Key& key, const Value& value)
+	:key_(key),value_(value),height_(1) {}
+	Node(const Tree& l, const Key& key, const Value& value, const Tree& r, size_t height)
+	:left_(l),key_(key),value_(value),right_(r),height_(height) {}
+	Node() {}
+};
+
+template <class Key, class Value>
+size_t height(const typename boost::shared_ptr<Node<Key,Value> >& t) {
+	if (t) return t->height_; else return 0;
+}
+
+template <class Key, class Value>
+typename Node<Key,Value>::Tree create(const typename Node<Key,Value>::Tree& l, const Key& key,
+		const Value& value, const typename Node<Key,Value>::Tree& r) {
+	size_t hl = height(l), hr = height(r);
+	size_t h = hl >= hr ? hl + 1 : hr + 1;
+	return typename Node<Key,Value>::Tree(new Node<Key, Value>(l,key,value,r, h));
+}
+
+template <class Key, class Value>
+typename Node<Key,Value>::Tree bal(const typename Node<Key,Value>::Tree& l, const Key& key,
+		const Value& value, const typename Node<Key,Value>::Tree& r) {
+	size_t hl = height(l), hr = height(r);
+	if(hl > hr+2) {
+		if(hl == 0) throw("Left tree is empty");
+		else if(l->left_->height_ >= l->right_->height_) {
+		  //  create ll lv ld (create lr x d r)
+			return create(l->left_,l->key_,l->value_, create(l->right_, key, value, r));
+		}
+		else{
+			if(l->right_->height_ == 0) throw("Left->Right is empty");
+			else {
+				 // create (create ll lv ld lrl) lrv lrd (create lrr x d r)
+				return create(
+						create(l->left_,l->key_,l->value_,l->right_->left_),
+						l->right_->key_,
+						l->right_->value_,
+						create(l->right_->right_,key,value,r));
+			}
+		}
+	}
+	else if (hr > hl + 2) {
+		if(hr == 0) throw("Right tree is empty");
+		else if(r->right_->height_ >= r->left_->height_) {
+			//  create (create l x d rl) rv rd rr
+			return create(create(l,key,value,r->left_),r->key_,r->value_,r);
+		}
+		else{
+			if(r->left_->height_ == 0) throw("Right->Left is empty");
+		  else {
+			  //  create (create l x d rll) rlv rld (create rlr rv rd rr)
+			  return create(
+			  		create(l,key,value,r->left_->left_),
+			  		r->left_->key_,
+			  		r->left_->value_,
+			  		create(r->left_->right_,r->key_,r->value_,r->right_));
+		  }
+		}
+	}
+	else {
+    return create(l,key,value,r);
+	}
+}
+
+template <class Key, class Value>
+typename Node<Key, Value>::Tree add(const Key& key, const Value& value, const typename Node<Key,Value>::Tree& tree) {
+	if(tree == NULL) {
+		return typename Node<Key,Value>::Tree(new Node<Key,Value>(key, value));
+	}
+	if(key == tree->key_) {
+		return typename Node<Key,Value>::Tree(new Node<Key, Value>(tree->left_, key, value, tree->right_, tree->height_));
+	}
+	else if( key < tree->key_) {
+		return bal(add(key, value, tree->left_), tree->key_, tree->value_, tree->right_);
+	}
+	else {
+		return bal(tree->left_, tree->key_, tree->value_, add(key, value, tree->right_));
+	}
+}
+
+template <class Key, class Value>
+Value find(const typename boost::shared_ptr<Node<Key,Value> >& tree, const Key& key){
+  if(tree->key_ == key)
+  	return tree->value_;
+  if(key < tree->key_)
+  	return find(tree->left_, key);
+  else
+  	return find(tree->right_,key);
+}
+
+}