The following is the whole process of creating this tree
1. Generate structure
The tree node contains a numerical field and two pointer fields, which point to the left and right children respectively.
Structure indication:
It is defined as follows:
struct TreeNode {
int val;
TreeNode* left;
TreeNode* right;
TreeNode() :val(0), left(nullptr), right(nullptr) {
}
TreeNode(int x) :val(x), left(nullptr), right(nullptr) {
}
TreeNode(int x, TreeNode* left, TreeNode* right) :val(x), left(left), right(right) {
}
};
2. Definition of the class
The root variable is encapsulated in the class BST , the root can be obtained using the getroot member function, and the function buildBST is declared .
class BST {
TreeNode* root;
public:
TreeNode* getroot()
{
return root;
}
void buildBST(vector<int>& vec);
};
3. Construction of the search tree
void BST::buildBST(vector<int>& vec) {
if (vec.size() == 0)
root = nullptr;//若为空树，则置空
root = new TreeNode(vec[0]);//创建根节点，并初始化为vec[0]
for (int i = 1; i < vec.size(); i++) {
TreeNode* newNode = new TreeNode(vec[i]);//创建节点
TreeNode* Root = root;//保存当前根节点,用Root寻找插入位置
while (Root) {
if (newNode->val < Root->val) {
//若小于根节点，放在节点左侧
if (Root->left == nullptr) {
//当根节点没有左孩子时，放置到此,此次插入结束，跳出循环
Root->left = newNode;
break;
}
Root = Root->left;//继续深入寻找
}
else {
if (Root->right == nullptr) {
Root->right = newNode;
break;
}
else {
Root = Root->right;
}
}
}
}
}
4. Print out search tree in middle order
According to the characteristics of the search tree, print it in the middle order to get a series of numbers from small to large.
The recursive method is used for in-order traversal:
void InOrderprint(TreeNode* root) {
//中序打印树
if (root == nullptr)
return;
InOrderprint(root->left);
cout << root->val << " ";
InOrderprint(root->right);
}
Complete code:
#include <iostream>
#include <vector>
using namespace std;
struct TreeNode {
int val;
TreeNode* left;
TreeNode* right;
TreeNode() :val(0), left(nullptr), right(nullptr) {
}
TreeNode(int x) :val(x), left(nullptr), right(nullptr) {
}
TreeNode(int x, TreeNode* left, TreeNode* right) :val(x), left(left), right(right) {
}
};
class BST {
TreeNode* root;
public:
TreeNode* getroot() {
return root;
}
void buildBST(vector<int>& vec);
};
void BST::buildBST(vector<int>& vec) {
if (vec.size() == 0)
root = nullptr;
root = new TreeNode(vec[0]);//创建根节点，并初始化为vec[0]
for (int i = 1; i < vec.size(); i++) {
TreeNode* newNode = new TreeNode(vec[i]);//创建节点
TreeNode* Root = root;//保存当前根节点,用Root寻找插入位置
while (Root) {
if (newNode->val < Root->val) {
//若小于根节点，放在节点左侧
if (Root->left == nullptr) {
//当根节点没有左孩子时，放置到此
Root->left = newNode;
break;
}
Root = Root->left;//继续深入寻找
}
else {
if (Root->right == nullptr) {
Root->right = newNode;
break;
}
else {
Root = Root->right;
}
}
}
}
}
void InOrderprint(TreeNode* root) {
//中序打印树
if (root == nullptr)
return;
InOrderprint(root->left);
cout << root->val << " ";
InOrderprint(root->right);
}
int main(int argc, char* argv[])
{
vector<int> vec = {
8,4,3,2,1,5,6,7 };
BST bst;
bst.buildBST(vec);
TreeNode* roo = bst.getroot();
InOrderprint(roo);
return 0;
}
Running effect chart:
