Creation of binary tree nodes
class TreeNode
{
public:
int value; // 所对应的值
TreeNode *left, *right; // 下一个结点的地址
TreeNode(int val)
{
value = val;
left = nullptr;
right = nullptr;
}
~TreeNode()
{
delete right;
delete left;
}
};
The binary tree constructed by sequential storage is converted into a chained storage binary tree
According to the relationship between the left subtree of the binary tree and the left subtree is the serial number of the root node:
- Root node serial number: i
- The number of the root node of the left subtree: i*2+1
- The root node number of the right subtree: i*2+2
The above relations are in an array in sequential storage.
step:
- Create an array to store the nodes of the binary tree and the root node
- Initialize the array of binary tree nodes
- Construct and convert the numerical array of formal parameters into a linked storage binary tree based on the relationship between the root node and the serial numbers of the left and right children
class BinaryTree
{
public:
// 将顺序存储的二叉树转换成链式存储的二叉树
static TreeNode *construct_BinaryTree(vector<int> nums)
{
// 创建存储二叉树结点的数组和根节点
TreeNode *root = nullptr;
vector<TreeNode *> vecTree(nums.size(), nullptr);
// 初始化二叉树数组
for (int i = 0; i < nums.size(); i++)
{
// 如果数组元素值不为-1则设置结点值
TreeNode *node = nullptr;
if (nums[i] != -1)
{
node = new TreeNode(nums[i]);
}
vecTree[i] = node;
// 如果是根节点则更新root的值
if (i == 0)
{
root = node;
/* code */
}
}
// 将存储二叉树子结点的数组转换成链式存储，
for (int i = 0; i * 2 + 1 < vecTree.size(); i++)
{
if (vecTree[i * 2 + 1] != nullptr)
{
vecTree[i]->left = vecTree[i * 2 + 1];
if (i * 2 + 2 < vecTree.size())
{
/* code */
vecTree[i]->right = vecTree[i * 2 + 2];
}
}
}
// 返回链式存储的二叉树根节点
return root;
}
// 前序遍历
static void PreTaverse(TreeNode *node)
{
if (node == nullptr)
{
return;
}
// 输出节点的值
cout << node->value << "\t";
// 访问左子树
PreTaverse(node->left);
// 访问右子树
PreTaverse(node->right);
}
// 中序遍历
static void MidTaverse(TreeNode *node)
{
if (node == nullptr)
{
return;
}
// 访问左子树
MidTaverse(node->left);
// 输出节点的值
cout << node->value << "\t";
// 访问右子树
MidTaverse(node->right);
}
// 后序遍历
static void BackTaverse(TreeNode *node)
{
if (node == nullptr)
{
return;
}
// 访问左子树
BackTaverse(node->left);
// 访问右子树
BackTaverse(node->right);
// 输出节点的值
cout << node->value << "\t";
}
};
traversal output test
Use the traversal method in the binary tree to verify the converted linked storage binary tree
int main(int argc, char const *argv[])
{
// 二叉树的数值数组
vector<int> nums = {
1, 2, 3, 4, 5, 6, 7};
TreeNode *root = BinaryTree::construct_BinaryTree(nums);
// 遍历输出
cout << "先序遍历：";
BinaryTree::PreTaverse(root);
cout << endl;
cout << "中序遍历：";
BinaryTree::MidTaverse(root);
cout << endl;
cout << "后序遍历：";
BinaryTree::BackTaverse(root);
cout << endl;
return 0;
}
Output result:
