二叉樹轉換為雙向環形鏈表

二叉樹的節點與雙向環形鏈表的節點類似，均含有兩個指向不同方向的指針，因此他們之間的轉化是可以實現的。下面介紹一種遞歸的實現方法。由於方法比較簡單，就直接上代碼了

二叉樹的建立

node* create(const string& s)
{
 node* res = new node;
 res->left = nullptr;
 res->right = nullptr;
 res->s = s;
 return res;
}
node* insert(node* root, const string& s)
{
 if(root == nullptr)
 {
  root = create(s);
  return root;
 }
 node* temp = root;
 while(temp!=nullptr)
 {
  if(temp->s > s)
  {
   if(temp->left == nullptr)
   {
    temp->left = create(s);
    return root;
   }
   else
    temp = temp->left;
  }
  else
  {
   if(temp->right == nullptr)
   {
    temp->right = create(s);
    return root;
   }
   temp = temp->right;
  }
 }
}

二叉樹轉換為鏈表

node* join_two_cycle(node* first, node* second)
{
 if(first == nullptr)
  return second;
 if(second == nullptr)
  return first;
 node* rail_first = first->left;
 node* rail_second = second->left;
 rail_first->right = second;
 second->left = rail_first;
 rail_second->right = first;
 first->left = rail_second;
 return first;
}
node* merge_to_list(node* x)
{
 if(x == nullptr)
  return nullptr;
 node* head_left = merge_to_list(x->left);
 node* head_right = merge_to_list(x->right);
 x->left = x;
 x->right = x;
 head_left = join_two_cycle(head_left,x);
 head_left = join_two_cycle(head_left,head_right);
 return head_left;
}

測試代碼

#include <iostream>
#include <string>
#include <fstream>
using namespace std;
struct node
{
 string s;
 node* left;
 node* right;
};
node* insert(node* root, const string& s);
node* merge_to_list(node* x);
void main()
{
 ifstream in("data.txt");
 if(!in.good())
 {
  cout<<"Error"<<endl;
  exit(0);
 }
 node* root = nullptr;
 while(!in.eof())
 {
  string s;
  in>>s;
  root = insert(root,s);
 }
 node* head;
 head = merge_to_list(root);
 node* end = head->left;
 node* temp = head;
 while(temp != end)
 {
  cout<<temp->s<<" ";
  temp = temp->right;
 }
 cout<<end->s<<endl;
}

二叉樹的常見問題及其解決程序 http://www.linuxidc.com/Linux/2013-04/83661.htm

【遞歸】二叉樹的先序建立及遍歷 http://www.linuxidc.com/Linux/2012-12/75608.htm

在JAVA中實現的二叉樹結構 http://www.linuxidc.com/Linux/2008-12/17690.htm

【非遞歸】二叉樹的建立及遍歷 http://www.linuxidc.com/Linux/2012-12/75607.htm

二叉樹遞歸實現與二重指針 http://www.linuxidc.com/Linux/2013-07/87373.htm

二叉樹先序中序非遞歸算法 http://www.linuxidc.com/Linux/2014-06/102935.htm

輕松搞定面試中的二叉樹題目 http://www.linuxidc.com/linux/2014-07/104857.htm