#include <iostream>
#include <algorithm>
#include <string>
#include <cmath>
#include <time.h>
using namespace std;
typedef struct Node {
int key,ltag,rtag;
Node *lchild,*rchild;
} Node;
Node *getNewNode(int key) {
Node *p=(Node*)malloc(sizeof(Node));
p->key=key;
p->ltag=p->rtag=0;
p->lchild=p->rchild=NULL;
return p;
}
Node *insert(Node *root,int key) {
if(!root)return getNewNode(key);
if(rand()%2)root->lchild=insert(root->lchild,key);
else root->rchild=insert(root->rchild,key);
return root;
}
void clear(Node *root) {
if(!root)return ;
clear(root->lchild);
clear(root->rchild);
free(root);
return ;
}
void pre_order(Node *root) {
if(!root)return ;
cout<<root->key<<" ";
if(!root->ltag)pre_order(root->lchild);
if(!root->rtag)pre_order(root->rchild);
return ;
}
void in_order(Node *root) {
if(!root)return ;
if(!root->ltag)in_order(root->lchild);
cout<<root->key<<" ";
if(!root->rtag)in_order(root->rchild);
return ;
}
void post_order(Node *root) {
if(!root)return ;
if(!root->ltag)post_order(root->lchild);
if(!root->rtag)post_order(root->rchild);
cout<<root->key<<" ";
return ;
}
Node *pre_node=NULL,*inorder_root=NULL;
void __build_inorder_thread(Node *root) {
if(!root)return ;
if(!root->ltag)__build_inorder_thread(root->lchild);
if(inorder_root==NULL)inorder_root=root;
if(root->lchild==NULL) {
root->lchild=pre_node;
root->ltag=1;
}
if(pre_node&&pre_node->rchild==NULL) {
pre_node->rchild=root;
pre_node->rtag=1;
}
pre_node=root;
if(!root->rtag)__build_inorder_thread(root->rchild);
return ;
}
void build_inorder_thread(Node *root) {
__build_inorder_thread(root);
pre_node->rchild=NULL;
pre_node->rtag=1;
return ;
}
Node *getNext(Node *root){
if(root->rtag==1)return root->rchild;
root=root->rchild;
while(root->ltag==0&&root->lchild)root=root->lchild;
return root;
}
int main() {
srand(time(0));
Node *root=NULL;
for(int i=0; i<10; i++) {
root=insert(root,rand()%100);
}
pre_node=inorder_root=NULL;
build_inorder_thread(root);
pre_order(root);
printf("\n");
in_order(root);
printf("\n");
post_order(root);
cout<<endl;
Node *node=inorder_root;
while(node) {
cout<<node->key<<" ";
node=getNext(node);
}
clear(root);
return 0;
}