二叉树的前序、中序、后序的实现（递归和非递归）

二叉树的前序遍历，中序遍历，后序遍历，层序遍历一直是笔试面试中常考的内容，这次自己都把实现了

写了一两个小时，算是总结过了，以后用的时候拿出来，如果写的不好的，希望大家指出来

#include <stdio.h>#include <stdlib.h>#include <iostream>#include <queue>#include <stack>using namespace std;typedef struct BiTree_Node{char data;struct BiTree_Node *left, *right;}BiTree_Node;void CreateBiTree(BiTree_Node **root){char x;scanf("\n%c",&x);if(x == '#')*root = NULL;else{*root = (BiTree_Node*)malloc(sizeof(BiTree_Node)); if(*root == NULL)printf("malloc error\n");(*root)->data = x;printf("please input %c left child\n", x);CreateBiTree(&((*root)->left));printf("please input %c right child\n", x);CreateBiTree(&((*root)->right));}}/*先序遍历*/void PreOrder(BiTree_Node *root){if(root == NULL)return ;printf("%c\n",root->data);PreOrder(root->left);PreOrder(root->right);}/*中序遍历*/void InOrder(BiTree_Node *root){if(root == NULL)return ;InOrder(root->left);printf("%c\n",root->data);InOrder(root->right);}/*后序遍历*/void PostOrder(BiTree_Node *root){if(root == NULL)return ;PostOrder(root->left);PostOrder(root->right);printf("%c\n",root->data);}/*节点个数*/int Node_Num(BiTree_Node *root){if(root == NULL)return 0;elsereturn 1 + Node_Num(root->left) + Node_Num(root->right);}/*树的深度*/int depth(BiTree_Node *root){if(root == NULL)return 0;intdl = depth(root->left);int dr = depth(root->right);return (dl>dr ? dl : dr) + 1;}/*先序遍历的非递归实现*/void PreOrder_nocur(BiTree_Node *root){if(root == NULL)return;stack <BiTree_Node*> BiTstack;BiTree_Node *node = (BiTree_Node*)malloc(sizeof(BiTree_Node));BiTstack.push(root);while(!BiTstack.empty()){node = BiTstack.top();printf("%c\n",node->data);BiTstack.pop();if(node->right != NULL)BiTstack.push(node->right);if(node->left != NULL)BiTstack.push(node->left);}}/*中序遍历的非递归实现*/void InOrder_nocur(BiTree_Node *root){if(root == NULL)return ;BiTree_Node *node = root;/*先把左孩子全部压入栈中*/stack<BiTree_Node*> BiTstack;while(node != NULL){BiTstack.push(node);node = node->left;}while(!BiTstack.empty()){node = BiTstack.top();printf("%c\n",node->data);BiTstack.pop();/*每一个孩子的右孩子如果存在，从它开始的左孩子开始入栈*/node = node->right;while(node != NULL){BiTstack.push(node);node = node->left;}}}/*后序遍历的非递归实现------双栈法*/void PostOrder_nocur(BiTree_Node *root){stack<BiTree_Node*> s1, s2;BiTree_Node *node = root;s1.push(node);while(!s1.empty()){node = s1.top();s1.pop();s2.push(node);if(node->right != NULL)s1.push(node->left);if(node->left != NULL)s1.push(node->right);}while(!s2.empty()){node = s2.top();s2.pop();printf("%c\n",node->data);}}/*层序遍历的实现*/void level_travel(BiTree_Node *root){BiTree_Node *node;queue<BiTree_Node *> BiTQ;BiTQ.push(root);while(!BiTQ.empty()){node = BiTQ.front();BiTQ.pop();printf("%c\n",node->data);if(node->left != NULL)BiTQ.push(node);if(node->right != NULL)BiTQ.push(node);}}int main(){BiTree_Node *root;int flag = 1;while(flag){printf("-----------------0.创建二叉树---------------------\n");printf("-----------------1.前序遍历-----------------------\n");printf("-----------------2.中序遍历-----------------------\n");printf("-----------------3.后序遍历-----------------------\n");printf("-----------------4.层序遍历-----------------------\n");printf("-----------------5.树的深度-----------------------\n");printf("-----------------6.节点个数-----------------------\n");printf("-----------------7.前序遍历非递归-----------------\n");printf("-----------------8.中序遍历非递归-----------------\n");printf("-----------------9.后序遍历非递归-----------------\n");int x, len, num;scanf("\n%d",&x);switch(x){case 0:printf("please input the root\n"); CreateBiTree(&root);break;case 1:PreOrder(root); break;case 2:InOrder(root); break;case 3:PostOrder(root);break;case 4:level_travel(root);break;case 5:len = depth(root);printf("depth:%d\n",len);break;case 6:num = Node_Num(root);printf("node num:%d\n",num);break;case 7:PreOrder_nocur(root);break;case 8:InOrder_nocur(root);break;case 9:PostOrder_nocur(root);break;default:flag = 0;break;}}return 0;}

以后遇到一些其他的问题再加上去