#include<iostream>
#include<stack>
#include<queue>
//节点结构体
struct Node{int value;Node * left;Node * right;Node(int value):value(value),left(NULL),right(NULL){}
};
//构建二叉树
void inertNode(Node *node,int value){if(value<=node->value){if(!node->left){node->left=new Node(value);}else{inertNode(node->left,value);}}else{if(!node->right){node->right=new Node(value);}else{inertNode(node->right,value);}}
}
//前序遍历递归实现
void preOrder(Node *node){if(node){std::cout<<node->value;preOrder(node->left);preOrder(node->right);}
}//前序遍历非递归实现
class Solution {public:vector<int> preorderTraversal(TreeNode* root) {            if (!root) return {};vector<int> res;stack<TreeNode*> s{{root}};while (!s.empty()) {TreeNode *t = s.top();s.pop();res.push_back(t->val);if (t->right) s.push(t->right);if (t->left) s.push(t->left);            }return res;}
};//中序遍历递归实现
void inOrder(Node *node){if(node){inOrder(node->left);std::cout<<node->value;inOrder(node->right);}
}
//中序遍历非递归实现
void inOrder1(Node *node){std::stack<Node *> nstack;Node *temp=node;while(temp||!nstack.empty()){if(temp){nstack.push(temp);temp=temp->left;}else{temp=nstack.top();std::cout<<temp->value;nstack.pop();temp=temp->right;}}
}//后序遍历递归实现
void posOrder(Node *node){if(node){posOrder(node->left);posOrder(node->right);std::cout<<node->value;}
}
//后序遍历非递归实现
void posOrder1(Node *node){if(node==NULL)return;std::stack<Node *> nstack1, nstack2;nstack1.push(node);while (!nstack1.empty()){Node *temp=nstack1.top();nstack1.pop();nstack2.push(temp);if(temp->left)nstack1.push(temp->left);if(temp->right)nstack1.push(temp->right);}while(!nstack2.empty()){std::cout<<nstack2.top()->value;nstack2.pop();}
}
//后序遍历非递归实现
class Solution {public:vector<int> postorderTraversal(TreeNode* root) {if (!root) return {};vector<int> res;stack<TreeNode*> s{{root}};while (!s.empty()) {TreeNode *t = s.top();s.pop();res.insert(res.begin(), t->val);if (t->left) s.push(t->left);if (t->right) s.push(t->right);}return res;}
};//广度优先遍历(层序遍历）
void broadOrder(Node *node){if(!node){return;}std::queue<Node *> qnodes;qnodes.push(node);while(!qnodes.empty()){Node * temp=qnodes.front();std::cout<<temp->value;qnodes.pop();if(temp->left){qnodes.push(temp->left);}if(temp->right){qnodes.push(temp->right);}}
}
int main(){int n;while(std::cin>>n){n--;int value;std::cin>>value;Node root(value);while(n--){int newValue;std::cin>>newValue;inertNode(&root,newValue);}std::cout<<"preOrder is:";preOrder(&root);std::cout<<std::endl;std::cout<<"inOrder is:";inOrder(&root);std::cout<<std::endl;std::cout<<"PosOrder is:";posOrder(&root);std::cout<<std::endl;std::cout<<"PreOrder without recursion is:";preOrder1(&root);std::cout<<std::endl;std::cout<<"inOrder without recursion is:";inOrder1(&root);std::cout<<std::endl;std::cout<<"PosOrder without recursion is:";posOrder1(&root);std::cout<<std::endl;std::cout<<"BroadOrder is:";broadOrder(&root);}
}---------------------
作者：叶赫那拉坤
来源：CSDN
原文：https://blog.csdn.net/u010558281/article/details/74276577
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