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数据结构学习——二叉树

news 来源：原创 2025/6/28 6:36:57

二叉树并且前/中/后序遍历

线索二叉树

二叉树并且前/中/后序遍历

//二叉树
#include<iostream>using namespace std;struct TreeNode{string data;TreeNode* leftchild;TreeNode* rightchild;
};/*
这里我就是尝试把节点的创建和连接写一起了
显然，这种写法在二叉树较大的时候会很麻烦
*/
void createTreeAndConnect(TreeNode*&root,string data,string direction,TreeNode* parent){TreeNode* newnode = new TreeNode;newnode->data = data;newnode->leftchild = NULL;newnode->rightchild = NULL;if(root==NULL){root = newnode;return;}else{if(parent!=NULL){TreeNode* temp = parent;if(direction=="left"){temp->leftchild = newnode;}else if(direction=="right"){temp->rightchild = newnode;}}else{cout<<"没有父节点"<<endl;}}    
}/*
选择另外一种写法，把节点的创建和连接分开还有一种思路就是createTree和connectTree用另外一种方法封装好
也就是第一种方法，但是定位可以自己发挥想象
*/TreeNode* createTree(string data){TreeNode* newnode = new TreeNode;newnode->data = data;newnode->leftchild = NULL;newnode->rightchild = NULL;return newnode;
}void connectTree(TreeNode* your_node,string direction,TreeNode* parent){TreeNode* temp = parent;if(parent!=NULL){if(direction=="left"){temp->leftchild = your_node;}else if(direction=="right"){temp->rightchild = your_node;}}else{cout<<"没有父节点"<<endl;}
}
//Preorder Traversal：前序便利
void preorder_traversal(TreeNode* root){if(root==NULL){return;}else{cout<<root->data<<endl;preorder_traversal(root->leftchild);preorder_traversal(root->rightchild);}
}//Inorder Traversal：中序遍历
void inorder_traversal(TreeNode* root){if(root==NULL){return;}else{inorder_traversal(root->leftchild);cout<<root->data<<endl;inorder_traversal(root->rightchild);}
}//Postorder Traversal：后序遍历
void postorder_traversal(TreeNode* root){if(root==NULL){return;}else{postorder_traversal(root->leftchild);postorder_traversal(root->rightchild);cout<<root->data<<endl;}
}int main(){
//这里的数字为满二叉树对应数字/*TreeNode* root = NULL;createTreeAndConnect(root,"1","",NULL);createTreeAndConnect(root,"2","left",root);createTreeAndConnect(root,"3","right",root);createTreeAndConnect(root,"4","left",root->leftchild);createTreeAndConnect(root,"5","right",root->leftchild);
*/TreeNode* root=createTree("1");TreeNode* node1=createTree("2");TreeNode* node2=createTree("3");TreeNode* node3=createTree("4");TreeNode* node4=createTree("5");TreeNode* node5=createTree("6");TreeNode* node6=createTree("9");TreeNode* node7=createTree("12");connectTree(node1,"left",root);connectTree(node2,"right",root);connectTree(node3,"left",node1);connectTree(node4,"right",node1);connectTree(node5,"left",node2);connectTree(node6,"right",node3);connectTree(node7,"left",node5);cout<<"前序"<<endl;preorder_traversal(root);cout<<"中序"<<endl;inorder_traversal(root);cout<<"后序"<<endl;postorder_traversal(root);return 0;
}

前序：

中序

后序

线索二叉树

//线索二叉树
//threaded:有线状图案装饰的
//left/righttag:为0则指向左右孩子，为1则代表指向前驱或后继
#include<iostream>using namespace std;struct TreeNode{string data;TreeNode* leftchild;TreeNode* rightchild;bool lefttag;bool righttag;
};TreeNode* createNode(string data){TreeNode* newnode = new TreeNode;newnode->leftchild = NULL;newnode->rightchild = NULL;newnode->lefttag = 0;newnode->righttag = 0;newnode->data = data;return newnode; 
}void connectNode(TreeNode* parent_npde,TreeNode* your_node,string direction){if(parent_npde == NULL){cout<<"Parent node is NULL"<<endl;return;}else{if(direction == "left"){parent_npde->leftchild = your_node;            }else if(direction == "right"){parent_npde->rightchild = your_node;}}
}void printTree(TreeNode* root){ if(root == NULL){return;}else{printTree(root->leftchild);cout<<root->data<<endl;printTree(root->rightchild);}
}/*
pre表示的是当前节点的前驱节点如果当前节点的左孩子为空，则将当前节点的左孩子指向前驱节点，lefttag置为1如果pre的节点的右孩子为空，pre的右节点指向当前节点，righttag置为1结构有点类似于便利的结构，反正就是改位置
*/
void inThread(TreeNode* root, TreeNode*& pre){if (root == NULL){return;}else{inThread(root->leftchild,pre);if(root->leftchild == NULL){root->leftchild = pre;root->lefttag = 1;}if(pre != NULL && pre->rightchild == NULL){pre->rightchild = root;pre->righttag = 1;}pre = root;//更新前驱节点inThread(root->rightchild,pre);}
}void changeThread(TreeNode* root){ TreeNode* pre=NULL;inThread(root,pre);
}void inOrder(TreeNode* root){TreeNode* temp = root;while(temp!=NULL){//找到最左子节点while(temp->lefttag == 0){temp = temp->leftchild;}cout<<temp->data<<endl;//沿着线索访问while(temp!=NULL&&temp->righttag == 1){temp = temp->rightchild;cout<<temp->data<<endl;}//移动到右子节点（righttag为0）temp = temp->rightchild;} 
}int main(){TreeNode* root=createNode("1");TreeNode* node1=createNode("2");TreeNode* node2=createNode("3");TreeNode* node3=createNode("4");TreeNode* node4=createNode("5");TreeNode* node5=createNode("6");TreeNode* node6=createNode("9");TreeNode* node7=createNode("12");connectNode(root,node1,"left");connectNode(root,node2,"right");connectNode(node1,node3,"left");connectNode(node1,node4,"right");connectNode(node2,node5,"left");connectNode(node3,node6,"right");connectNode(node5,node7,"left");cout<<"中序便利"<<endl;printTree(root);cout<<"中序线索化"<<endl;changeThread(root);inOrder(root);return 0;}