首先定义树的节点：

struct BinaryTreeNode 
{int                    m_nValue; BinaryTreeNode*        m_pLeft;  BinaryTreeNode*        m_pRight; 
};

定义构建节点和连接节点的方法：

BinaryTreeNode* CreateBinaryTreeNode(int value)
{BinaryTreeNode* pNode = new BinaryTreeNode();pNode->m_nValue = value;pNode->m_pLeft = nullptr;pNode->m_pRight = nullptr;return pNode;
}void ConnectTreeNodes(BinaryTreeNode* pParent, BinaryTreeNode* pLeft, BinaryTreeNode* pRight)
{if(pParent != nullptr){pParent->m_pLeft = pLeft;pParent->m_pRight = pRight;}
}

 构建二叉树实例：

//              1
//            /   \
//           2     3
//       /       \
//      4         5
//     / \      /   \
//    6   7    8     9
void Test1()
{TreeNode* pNode1 = CreateTreeNode(1);TreeNode* pNode2 = CreateTreeNode(2);TreeNode* pNode3 = CreateTreeNode(3);TreeNode* pNode4 = CreateTreeNode(4);TreeNode* pNode5 = CreateTreeNode(5);TreeNode* pNode6 = CreateTreeNode(6);TreeNode* pNode7 = CreateTreeNode(7);TreeNode* pNode8 = CreateTreeNode(8);TreeNode* pNode9 = CreateTreeNode(9);ConnectTreeNodes(pNode1, pNode2);ConnectTreeNodes(pNode1, pNode3);ConnectTreeNodes(pNode2, pNode4);ConnectTreeNodes(pNode2, pNode5);ConnectTreeNodes(pNode4, pNode6);ConnectTreeNodes(pNode4, pNode7);ConnectTreeNodes(pNode5, pNode8);ConnectTreeNodes(pNode5, pNode9);
}