我正在尝试使用unique_ptr
实现二叉搜索树。 我已经用shared_ptr
编写了一个工作程序。 如果我想使用unique_ptr
来强制执行BinarySearchTree的单一所有权语义,该怎么办?
当我将shared_ptr
替换为unique_ptr
时,我遇到了超出我的理解范围的编译错误。
#include <iostream>
#include <memory>
template<class T>
class BinarySearchTree{
struct TreeNode;
typedef std::shared_ptr<TreeNode> spTreeNode;
struct TreeNode{
T data;
spTreeNode left;
spTreeNode right;
TreeNode(const T & value):data(value),left(nullptr),right(nullptr){}
};
spTreeNode root;
bool insert(spTreeNode node);
void print(const spTreeNode) const ;
public:
BinarySearchTree();
void insert( const T & node);
void print()const;
};
template<class T>
BinarySearchTree<T>::BinarySearchTree():root(nullptr){}
template<class T>
void BinarySearchTree<T>::insert(const T & ref)
{
TreeNode *node = new TreeNode(ref);
if (root==nullptr)
{
root.reset(node);
}
else
{
spTreeNode temp = root;
spTreeNode prev = root;
while (temp)
{
prev = temp;
if (temp->data < ref)
temp = temp->right;
else
temp = temp->left;
}
if (prev->data < ref)
prev->right.reset(node);
else
prev->left.reset(node);
}
}
template<class T>
void BinarySearchTree<T>::print()const
{
print(root);
}
template<class T>
void BinarySearchTree<T>::print(const spTreeNode node)const
{
if (node==nullptr)
return;
print(node->left);
std::cout << node->data<< std::endl;
print(node->right);
}
int main()
{
BinarySearchTree<int> bst;
bst.insert(13);
bst.insert(3);
bst.insert(5);
bst.insert(31);
bst.print();
return 0;
}
编辑:如果有人感兴趣,这里提供编译错误信息。警告:文本堆积如山。
prog.cpp: In instantiation of ‘void BinarySearchTree<T>::insert(const T&) [with T = int]’:
prog.cpp:75:18: required from here
prog.cpp:39:27: error: use of deleted function ‘std::unique_ptr<_Tp, _Dp>::unique_ptr(const std::unique_ptr<_Tp, _Dp>&) [with _Tp = BinarySearchTree<int>::TreeNode; _Dp = std::default_delete<BinarySearchTree<int>::TreeNode>]’
spTreeNode temp = root;
^
In file included from /usr/include/c++/4.8/memory:81:0,
from prog.cpp:2:
/usr/include/c++/4.8/bits/unique_ptr.h:273:7: error: declared here
unique_ptr(const unique_ptr&) = delete;
^
prog.cpp:40:27: error: use of deleted function ‘std::unique_ptr<_Tp, _Dp>::unique_ptr(const std::unique_ptr<_Tp, _Dp>&) [with _Tp = BinarySearchTree<int>::TreeNode; _Dp = std::default_delete<BinarySearchTree<int>::TreeNode>]’
spTreeNode prev = root;
^
In file included from /usr/include/c++/4.8/memory:81:0,
from prog.cpp:2:
/usr/include/c++/4.8/bits/unique_ptr.h:273:7: error: declared here
unique_ptr(const unique_ptr&) = delete;
^
prog.cpp:43:18: error: use of deleted function ‘std::unique_ptr<_Tp, _Dp>& std::unique_ptr<_Tp, _Dp>::operator=(const std::unique_ptr<_Tp, _Dp>&) [with _Tp = BinarySearchTree<int>::TreeNode; _Dp = std::default_delete<BinarySearchTree<int>::TreeNode>]’
prev = temp;
^
In file included from /usr/include/c++/4.8/memory:81:0,
from prog.cpp:2:
/usr/include/c++/4.8/bits/unique_ptr.h:274:19: error: declared here
unique_ptr& operator=(const unique_ptr&) = delete;
^
prog.cpp:45:22: error: use of deleted function ‘std::unique_ptr<_Tp, _Dp>& std::unique_ptr<_Tp, _Dp>::operator=(const std::unique_ptr<_Tp, _Dp>&) [with _Tp = BinarySearchTree<int>::TreeNode; _Dp = std::default_delete<BinarySearchTree<int>::TreeNode>]’
temp = temp->right;
^
In file included from /usr/include/c++/4.8/memory:81:0,
from prog.cpp:2:
/usr/include/c++/4.8/bits/unique_ptr.h:274:19: error: declared here
unique_ptr& operator=(const unique_ptr&) = delete;
^
prog.cpp:47:22: error: use of deleted function ‘std::unique_ptr<_Tp, _Dp>& std::unique_ptr<_Tp, _Dp>::operator=(const std::unique_ptr<_Tp, _Dp>&) [with _Tp = BinarySearchTree<int>::TreeNode; _Dp = std::default_delete<BinarySearchTree<int>::TreeNode>]’
temp = temp->left;
^
In file included from /usr/include/c++/4.8/memory:81:0,
from prog.cpp:2:
/usr/include/c++/4.8/bits/unique_ptr.h:274:19: error: declared here
unique_ptr& operator=(const unique_ptr&) = delete;
^
prog.cpp: In instantiation of ‘void BinarySearchTree<T>::print() const [with T = int]’:
prog.cpp:79:15: required from here
prog.cpp:59:15: error: use of deleted function ‘std::unique_ptr<_Tp, _Dp>::unique_ptr(const std::unique_ptr<_Tp, _Dp>&) [with _Tp = BinarySearchTree<int>::TreeNode; _Dp = std::default_delete<BinarySearchTree<int>::TreeNode>]’
print(root);
^
In file included from /usr/include/c++/4.8/memory:81:0,
from prog.cpp:2:
/usr/include/c++/4.8/bits/unique_ptr.h:273:7: error: declared here
unique_ptr(const unique_ptr&) = delete;
^
prog.cpp:63:6: error: initializing argument 1 of ‘void BinarySearchTree<T>::print(BinarySearchTree<T>::spTreeNode) const [with T = int; BinarySearchTree<T>::spTreeNode = std::unique_ptr<BinarySearchTree<int>::TreeNode, std::default_delete<BinarySearchTree<int>::TreeNode> >]’
void BinarySearchTree<T>::print(const spTreeNode node)const
^
unique_ptr
只能被移动。 - QuentinTreeNode*
(无所有权),而不是unique_ptr<TreeNode>
(独占所有权)。树拥有所有权,而非遍历它的代码。 - Ben Voigt