/*求二叉樹鏡像 -- 采用遞歸和非遞歸方法
經(jīng)調(diào)試可運(yùn)行源碼及分析如下：
***/
#include <stdlib.h>
#include <iostream>
#include <queue>
using std::cout;
using std::cin;
using std::endl;
using std::queue;
/*二叉樹結(jié)點(diǎn)定義*/
typedef struct BTreeNode
{
  char elem;
  struct BTreeNode *pleft;
  struct BTreeNode *pright;
}BTreeNode;
/*
求二叉樹鏡像
遞歸方式步驟：
如果proot為NULL，則為空樹，返回；
如果proot不為NULL，交換proot左右結(jié)點(diǎn)，然后分別求左右子樹的鏡像；
*/
/*遞歸求二叉樹鏡像*/
void get_bitree_mirror(BTreeNode* proot)
{
  if (proot == NULL)
    return ;
  BTreeNode* temp_node = proot->pleft;
  proot->pleft = proot->pright;
  proot->pright = temp_node;
  get_bitree_mirror(proot->pleft);
  get_bitree_mirror(proot->pright);
  return ;
}
/*
非遞歸方式步驟如下：
借助隊(duì)列
首先，將根節(jié)點(diǎn)proot入隊(duì)；
第一步：當(dāng)隊(duì)列非空時(shí)，獲取當(dāng)前層次的節(jié)點(diǎn)總數(shù)，即當(dāng)前隊(duì)列的長度；執(zhí)行第二步；
第二步：按照當(dāng)前層的節(jié)點(diǎn)總數(shù)，出隊(duì)進(jìn)行遍歷節(jié)點(diǎn)，在遍歷時(shí)，
    交換左右節(jié)點(diǎn)，如果左右節(jié)點(diǎn)存在，則入隊(duì)；
    當(dāng)遍歷完當(dāng)前層所有節(jié)點(diǎn)時(shí)，遍歷下一層，執(zhí)行第一步。
*/
void get_bitree_mirror_leveltraverse(BTreeNode* proot)
{
  if(proot == NULL)
    return ;
  queue <BTreeNode*> que;
  que.push(proot);
  int level_nodes_number = 0;
  while (!que.empty())//層次遍歷
  {
    level_nodes_number = que.size();
    int level_count = 0;
    while (level_count < level_nodes_number)
    {
      ++level_count;
      proot = que.front();
      que.pop();
      //交換左右子節(jié)點(diǎn)
      BTreeNode* temp_node = proot->pleft;
      proot->pleft = proot->pright;
      proot->pright = temp_node;
      if(proot->pleft != NULL)
        que.push(proot->pleft);
      if(proot->pright != NULL)
        que.push(proot->pright);
    }
  }
  return ;
}
/*初始化二叉樹根節(jié)點(diǎn)*/
BTreeNode* btree_init(BTreeNode* &bt)
{
  bt = NULL;
  return bt;
}
/*先序創(chuàng)建二叉樹*/
void pre_crt_tree(BTreeNode* &bt)
{
  char ch;
  cin >> ch;
  if (ch == '#')
  {
    bt = NULL;
  }
  else
  {
    bt = new BTreeNode;
    bt->elem = ch;
    pre_crt_tree(bt->pleft);
    pre_crt_tree(bt->pright);
  }
}
/*先序遍歷*/
void pre_order_traverse(BTreeNode* proot)
{
  if(proot == NULL)
    return;
  cout<< proot->elem << " ";
  pre_order_traverse(proot->pleft);
  pre_order_traverse(proot->pright);
  return;
}
int main()
{
  int tree_node_number = 0;
  BTreeNode *bt;
  btree_init(bt);//初始化根節(jié)點(diǎn)
  pre_crt_tree(bt);//創(chuàng)建二叉樹
  cout << "先序遍歷輸出如下：" << endl;
  cout << "調(diào)用鏡像函數(shù)前：" << endl;
  pre_order_traverse(bt);
  cout << endl;
  get_bitree_mirror(bt);
  cout << "遞歸調(diào)用鏡像函數(shù)后：" << endl;
  pre_order_traverse(bt);
  cout << endl;
  cout << "非遞歸調(diào)用鏡像函數(shù)后：" << endl;
  get_bitree_mirror_leveltraverse(bt);
  pre_order_traverse(bt);
  cout << endl;
  system("pause");
  return 0;
}

/*
運(yùn)行結(jié)果：
a b c # # # d e # # #
------以上為輸入-----------
------以下為輸出-----------
先序遍歷輸出如下：
調(diào)用鏡像函數(shù)前：
a b c d e
遞歸調(diào)用鏡像函數(shù)后：
a d e b c
非遞歸調(diào)用鏡像函數(shù)后：
a b c d e
請按任意鍵繼續(xù). . .
---------------------------------
本例創(chuàng)建的二叉樹形狀：
    a
  b    d
c     e
調(diào)用遞歸求二叉樹鏡像形狀：
   a
d    b
  e    c
再次調(diào)用非遞歸求二叉樹鏡像形狀（即鏡像的鏡像）:
    a
  b    d
c     e
*/