二分搜索树

Author: tianqing.liang

README.md

@@ -11,7 +11,7 @@
 7. **[Dart,Python]归并排序**
 8. **[Dart,Python]快速排序**
 9. **[Dart,Python]二分搜索**
-10. 二分搜索树
+10. **[Dart,Python]二分搜索树**
 11. 集合 和 映射
 12. 堆
 13. 优先队列

python/BST.py

@@ -0,0 +1,106 @@
+class BSTNode(object):
+    def __init__(self, key, value, left=None, right=None):
+        self.key, self.value, self.left, self.right = key, value, left, right
+
+
+class BST(object):
+    def __init__(self, root=None):
+        self.root = root
+
+    @classmethod
+    def build_from(cls, node_list):
+        cls.size = 0
+        key_to_node_dict = {}
+        for node_dict in node_list:
+            key = node_dict['key']
+            key_to_node_dict[key] = BSTNode(key, value=key) 
+
+        for node_dict in node_list:
+            key = node_dict['key']
+            node = key_to_node_dict[key]
+            if node_dict['is_root']:
+                root = node
+            node.left = key_to_node_dict.get(node_dict['left'])
+            node.right = key_to_node_dict.get(node_dict['right'])
+            cls.size += 1
+        return cls(root)
+
+    def _bst_search(self, subtree, key):
+        if subtree is None:  
+            return None
+        elif key < subtree.key:
+            return self._bst_search(subtree.left, key)
+        elif key > subtree.key:
+            return self._bst_search(subtree.right, key)
+        else:
+            return subtree
+
+    def __contains__(self, key):
+        return self._bst_search(self.root, key) is not None
+
+    def get(self, key, default=None):
+        node = self._bst_search(self.root, key)
+        if node is None:
+            return default
+        else:
+            return node.value
+
+    def _bst_min_node(self, subtree):
+        if subtree is None:
+            return None
+        elif subtree.left is None:  
+            return subtree
+        else:
+            return self._bst_min_node(subtree.left)
+
+    def bst_min(self):
+        node = self._bst_min_node(self.root)
+        return node.value if node else None
+
+    def _bst_insert(self, subtree, key, value):
+        
+        if subtree is None:   
+            subtree = BSTNode(key, value)
+        elif key < subtree.key:
+            subtree.left = self._bst_insert(subtree.left, key, value)
+        elif key > subtree.key:
+            subtree.right = self._bst_insert(subtree.right, key, value)
+        return subtree
+
+    def add(self, key, value):
+        node = self._bst_search(self.root, key)
+        if node is not None:  
+            node.value = value
+            return False
+        else:
+            self.root = self._bst_insert(self.root, key, value)
+            self.size += 1
+            return True
+
+    def _bst_remove(self, subtree, key):
+        if subtree is None:
+            return None
+        elif key < subtree.key:
+            subtree.left = self._bst_remove(subtree.left, key)
+            return subtree
+        elif key > subtree.key:
+            subtree.right = self._bst_remove(subtree.right, key)
+            return subtree
+        else:  # 找到了需要删除的节点
+            if subtree.left is None and subtree.right is None:    # 叶节点，返回 None 把其父亲指向它的指针置为 None
+                return None
+            elif subtree.left is None or subtree.right is None:  # 只有一个孩子
+                if subtree.left is not None:
+                    return subtree.left   # 返回它的孩子并让它的父亲指过去
+                else:
+                    return subtree.right
+            else:  # 俩孩子，寻找后继节点替换，并删除其右子树的后继节点，同时更新其右子树
+                successor_node = self._bst_min_node(subtree.right)
+                subtree.key, subtree.value = successor_node.key, successor_node.value
+                subtree.right = self._bst_remove(subtree.right, successor_node.key)
+                return subtree
+
+    def remove(self, key):
+        assert key in self
+        self.size -= 1
+        return self._bst_remove(self.root, key)

python/linkedlist.py

@@ -7,7 +7,9 @@ def __init__(self,value):
     def __str__(self):
         return self.value;
 
-
+'''
+    链表
+'''
 class LinkedList(object):
 
     def __init__(self):

python/loopqueue.py

@@ -1,3 +1,6 @@
+'''
+    循环队列
+'''
 class LoopQueue(object):
 
     def __init__(self, n=10):