二叉树前中后序遍历

本文主要是介绍二叉树前中后序遍历，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

前言

个人小记

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一、代码如下

#include<stdio.h>
#include <stdlib.h>
#include <time.h>
#define MAX_NODE 10
#define p()\
{\printf("\n");\
}
typedef struct Node
{int key;int lfag,rfag;struct Node *lchild,*rchild;
}Node;Node* init_node(int key)
{Node* node=(Node*)malloc(sizeof(Node));node->key=key;node->lfag=node->rfag=0;node->lchild=node->rchild=NULL;return node;
}Node* insert(Node* root,int key)
{if(root==NULL)return init_node(key);if(rand()%2) root->lchild=insert(root->lchild,key);else root->rchild=insert(root->rchild,key);return root;
}void clear_node(Node* root)
{if(root==NULL)return ;if(root->lfag==0) clear_node(root->lchild);if(root->rfag==0) clear_node(root->rchild);free(root);return ;
}void pre_order(Node* root)
{if(root==NULL)return ;printf("%d ",root->key);if(root->lfag==0)pre_order(root->lchild);if(root->rfag==0)pre_order(root->rchild);return ;
}void in_order(Node* root)
{if(root==NULL)return ;if(root->lfag==0)in_order(root->lchild);printf("%d ",root->key);if(root->rfag==0)in_order(root->rchild);return ;
}void post_order(Node* root)
{if(root==NULL)return ;if(root->lfag==0)post_order(root->lchild);if(root->rfag==0)post_order(root->rchild);printf("%d ",root->key);return ;
}
Node* new_root=NULL,*pre_node;
void __serial_in_order(Node* root)
{if(root==NULL)return ;if(root->lfag==0)__serial_in_order(root->lchild);if(new_root==NULL)new_root=root;if(root->lchild==NULL){root->lchild=pre_node;root->lfag=1;}if(pre_node&&pre_node->rchild==NULL){pre_node->rchild=root;pre_node->rfag=1;}pre_node=root;if(root->rfag==0)__serial_in_order(root->rchild);return ;
}void serial_in_order(Node*root)
{__serial_in_order(root);pre_node->rchild=NULL;pre_node->rfag=1;return ;
}Node* getnext(Node* node)
{if(node->rfag==1)return node->rchild;node=node->rchild;while(node->lfag==0){node=node->lchild;}return node;
}int main()
{srand((unsigned)time(0));Node* root=NULL;for(int i=0;i<MAX_NODE;i++){root=insert(root,rand()%100);}serial_in_order(root);Node* node=new_root;printf("中序线索化遍历结果为:\n");while(node){printf("%d ",node->key);node=getnext(node);}p();printf("前序遍历结果为:\n");pre_order(root);  p();printf("中序遍历结果为:\n");in_order(root);   p();printf("后续遍历结果为:\n");post_order(root); p();clear_node(root);return 0;
}

二、测试结果

中序线索化遍历结果为:
76 99 23 86 70 59 38 50 28 4 
前序遍历结果为:
86 76 23 99 50 38 70 59 4 28 
中序遍历结果为:
76 99 23 86 70 59 38 50 28 4 
后续遍历结果为:
99 23 76 59 70 38 28 4 50 86 

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