树的操作（完）

 

/*
-------------------------------------------------
   Author:       wry
   date:         2022/2/24 11:22
   Description:  Tree
-------------------------------------------------
*/

#include <bits/stdc++.h>

using namespace std;

struct TreeNode {
    char data;
    TreeNode *left;
    TreeNode *right;
    TreeNode(char d):data(d),left(nullptr),right(nullptr) {}
};

//二叉排序树的插入值
TreeNode* Insert(TreeNode *root,char d) {
    if (root == nullptr) {
        root = new TreeNode(d);
    }
    else {
        if (d < root->data) {
            root->left = Insert(root->left,d);
        }
        else if (d > root->data){
            root->right = Insert(root->right,d);
        }
    }
    return root;
}

//先序排序
void PreOrder (TreeNode* root) {
    if (root == nullptr) {
        return ;
    }
    printf ("%c ",root->data);
    PreOrder(root->left);
    PreOrder(root->right);
    return ;
}

//中序排序
void InOrder (TreeNode* root) {
    if (root == nullptr) {
        return ;
    }
    InOrder(root->left);
    printf ("%c ",root->data);
    InOrder(root->right);
    return ;
}

//后序排序
void PostOrder (TreeNode* root) {
    if (root == nullptr) {
        return ;
    }
    PostOrder(root->left);
    PostOrder(root->right);
    printf ("%c ",root->data);
    return ;
}

//层序遍历
void LevelOrder(TreeNode* root) {
    if (root==nullptr) {
        return ;
    }
    tree.push(root);
    while (tree.size()!=0) {
        cout << tree.front()->data << " ";
        if (tree.front()->lchild!= nullptr) {
            tree.push(tree.front()->lchild);
        }
        if (tree.front()->rchild!= nullptr) {
            tree.push(tree.front()->rchild);
        }
        tree.pop();
    }
    return ;
}

//通过先序+中序序列（字符串），构造树
TreeNode* PreAndInBuild (string preorder,string inorder) {
    if (preorder.size() == 0) {
        return nullptr;
    }
    char c = preorder[0];
    TreeNode* root = new TreeNode(c);     //为此值创建一个结点
    int position = inorder.find(c);     //找到c在inorder出现的位置（下标值）
    root->left = PreAndInBuild(preorder.substr(1,position),inorder.substr(0,position));
    root->right = PreAndInBuild(preorder.substr(position+1),inorder.substr(position+1));    //表示从下标positio+1开始到结尾
    return root;
}

//后序+中序
TreeNode* PostAndInBuild (string postorder,string inorder) {
    if (postorder.size()==0) {
        return nullptr;
    }
    char c = postorder[postorder.size()-1];
    TreeNode* root = new TreeNode(c);
    int position = inorder.find(c);
    root->left = PostAndInBuild(postorder.substr(0,position),inorder.substr(0,position));
    root->right = PostAndInBuild(postorder.substr(position,inorder.size()-position-1),inorder.substr(position+1));
    return root;
}

int main() {
    string levelorder = "ABCDE";
    string inorder = "ACBED";
    TreeNode* root = LevelAndInBuild(levelorder,inorder);
    PreOrder(root);
    return 0;
}

 

二叉树的构造、三种遍历、根据遍历构建二叉树、二叉排序树的插入生成......