ds: Update binary tree interface

ds/4.tree/CMakeLists.txt

@@ -1,5 +1,5 @@
 
-add_library(linked-binary-tree
+add_library(linked-binary-tree-static STATIC
     linked_binary_tree.c
     binary_tree.h
     )

ds/4.tree/binary_tree.h

@@ -2,9 +2,11 @@
 // Use of this source is governed by GNU General Public License
 // that can be found in the LICENSE file.
 
-#ifndef DATA_STRUCTURES_3_TREE_BINARY_TREE_H_
-#define DATA_STRUCTURES_3_TREE_BINARY_TREE_H_
+#ifndef BINARY_TREE_H_
+#define BINARY_TREE_H_
 
+#include <stdbool.h>
+#include <stddef.h>
 #include <stdint.h>
 
 #ifdef __cplusplus
@@ -13,13 +15,49 @@ extern "C" {
 
 typedef struct binary_tree_s binary_tree_t;
 
-#define element_type int32_t
-
-binary_tree_t* binary_tree_new();
-void binary_tree_free(binary_tree_t* tree);
+/**
+ * Create an empty binary tree.
+ *
+ * @return
+ */
+extern binary_tree_t* binary_tree_new();
+
+/**
+ * Deallocate tree nodes in binary tree and free the binary tree descriptor.
+ *
+ * @param tree
+ */
+extern void binary_tree_free(binary_tree_t* tree);
+
+/**
+ * Get number of elements in binary tree.
+ *
+ * @param tree
+ * @return
+ */
+extern size_t binary_tree_size(binary_tree_t* tree);
+
+/**
+ * Returns true if binary tree has no node.
+ *
+ * @param tree
+ * @return
+ */
+extern bool binary_tree_is_empty(binary_tree_t* tree);
+
+/**
+ * Calls |apply| function for each node in binary tree.
+ *
+ * @param tree
+ * @param apply
+ * @param user_data
+ */
+extern void binary_tree_traverse(binary_tree_t* tree,
+                                 void (*apply)(void* value, void* user_data),
+                                 void* user_data);
 
 #ifdef __cplusplus
 }
 #endif
 
-#endif  // DATA_STRUCTURES_3_TREE_BINARY_TREE_H_
+#endif  // BINARY_TREE_H_

ds/4.tree/linked_binary_tree.c

@@ -6,25 +6,43 @@
 
 #include <assert.h>
 #include <stddef.h>
+#include <stdlib.h>
 #include <string.h>
 
 typedef struct tree_node_s tree_node_t;
 
 struct tree_node_s {
   tree_node_t* left;
   tree_node_t* right;
-  element_type value;
+  void* value;
 };
 
 struct binary_tree_s {
-  tree_node_t* root;
   size_t size;
+  tree_node_t* root;
 };
 
 binary_tree_t* binary_tree_new() {
+  binary_tree_t* tree = malloc(sizeof(binary_tree_t));
+  assert(tree != NULL);
+  tree->size = 0;
+  tree->root = NULL;
 
+  return tree;
 }
 
 void binary_tree_free(binary_tree_t* tree) {
-
+  assert(tree != NULL);
+  // TODO(Shaohua): deallocate tree nodes.
+  free(tree);
+}
+
+size_t binary_tree_size(binary_tree_t* tree) {
+  assert(tree != NULL);
+  return tree->size;
+}
+
+bool binary_tree_is_empty(binary_tree_t* tree) {
+  assert(tree != NULL);
+  return tree->size > 0;
 }