change bst interface

Author: xtaci

include/binary_search_tree.h

@@ -23,6 +23,8 @@
 
 #include <stdlib.h>
 #include <stdint.h>
+#include <exception>
+
 namespace alg
 {
 template<typename KeyT, typename ValueT>
@@ -39,9 +41,19 @@ namespace alg
 treeNode *left;// left child
 treeNode *right;// right child
 };
+
+class BSTException: public std::exception
+{
+public:
+virtual const char * what() const throw()
+{
+return "key does not exist";
+}
+};
 
 private:
 treeNode * m_root;
+BSTException error;
 
 public:
 BST():m_root(NULL){};
@@ -53,16 +65,36 @@ namespace alg
 
 ValueT operator[] (const KeyT & key)
 {
-if (m_root == NULL) return NULL;
+if (m_root == NULL) throw error;
 treeNode * tmp = m_root;
 
 while(true) {
 if (key == tmp->key) return tmp->value;
 else if(key < tmp->key) {
-if (tmp->left == NULL) return NULL;
+if (tmp->left == NULL) throw error;
+tmp = tmp->left;
+} else {
+if (tmp->right == NULL) throw error;
+tmp = tmp->right;
+}
+}
+}
+
+/**
+ * test whether the key is in the tree
+ */
+bool contains(const KeyT & key)
+{
+if (m_root == NULL) return false;
+treeNode * tmp = m_root;
+
+while(true) {
+if (key == tmp->key) return true;
+else if(key < tmp->key) {
+if (tmp->left == NULL) return false;
 tmp = tmp->left;
 } else {
-if (tmp->right == NULL) return NULL;
+if (tmp->right == NULL) return false;
 tmp = tmp->right;
 }
 }

src/binary_search_tree_demo.cpp

@@ -30,5 +30,11 @@ int main()
 for(i = 0; i < MAX_ELEMENTS; i++){
 printf("getting %d->%d\n",key[i], t[key[i]]);
 }
+
+for(i = 0; i < MAX_ELEMENTS; i++){
+int k = rand()%100;
+printf("testing %d-> %s\n",k,t.contains(k)?"YES":"NO");
+}
+
 return 0;
 }