利用栈实现二叉树的先序，中序，后序遍历的非递归操作

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1. #include <stdio.h>  
2. #include <malloc.h>  
3. #include <stdlib.h>  
4. #include <queue>  
5. #include <stack>  
6. #include <iostream>  
7. using namespace std;  
8. typedef struct BiTNode{  
9.     char data;  
10.     BiTNode *lchild, *rchild;  
11. }BiTNode,*BiTree;  
12.   
13. void CreateBiTree(BiTree &T)//建树，按先序顺序输入节点  
14. {  
15.     char ch;  
16.     scanf("%c",&ch);  
17.     if(ch==' ')  
18.     {  
19.         T=NULL;  
20.         return;  
21.     }  
22.     else  
23.     {  
24.         T=(BiTree)malloc(sizeof(BiTNode));  
25.         if(!T)  
26.             exit(1);  
27.         T->data=ch;  
28.         CreateBiTree(T->lchild);  
29.         CreateBiTree(T->rchild);  
30.     }  
31. }  
32. void InOrderTraverse(BiTree T)//非递归中序遍历  
33. {  
34.       
35.     stack<BiTree> Stack;  
36.     if(!T)  
37.     {  
38.         printf("空树！\n");  
39.         return;  
40.     }  
41.       
42.     while(T || !Stack.empty())  
43.     {  
44.         while(T)  
45.         {  
46.             Stack.push(T);  
47.             T=T->lchild;  
48.         }  
49.         T=Stack.top();  
50.         Stack.pop();  
51.         printf("%c",T->data);  
52.         T=T->rchild;  
53.     }                                                                                                                                     
54. }  
55.   
56.   
57.   
58. void PreOrderTraverse(BiTree T)//非递归先序遍历  
59. {  
60.       
61.     stack<BiTree> Stack;  
62.     if(!T)  
63.     {  
64.         printf("空树！\n");  
65.         return;  
66.     }  
67.     while(T || !Stack.empty())  
68.     {  
69.         while(T)  
70.         {  
71.             Stack.push(T);  
72.             printf("%c",T->data);  
73.             T=T->lchild;  
74.         }  
75.         T=Stack.top();  
76.         Stack.pop();          
77.              T=T->rchild;          
78.     }                                                                                                                                     
79. }  
80.   
81.   
82. void PostOrderTraverse(BiTree T)//非递归后序遍历,用一个标记标记右子树是否访问过  
83. {  
84.     int flag[20];  
85.     stack<BiTree> Stack;  
86.     if(!T)  
87.     {  
88.         printf("空树！\n");  
89.         return;  
90.     }  
91.     while(T)  
92.     {  
93.         Stack.push(T);  
94.         flag[Stack.size()]=0;  
95.         T=T->lchild;  
96.     }  
97.     while(!Stack.empty())  
98.     {  
99.         T=Stack.top();            
100.         while(T->rchild && flag[Stack.size()]==0)  
101.         {  
102.             flag[Stack.size()]=1;  
103.             T=T->rchild;  
104.             while(T)  
105.             {  
106.                 Stack.push(T);  
107.                 flag[Stack.size()]=0;  
108.                 T=T->lchild;  
109.             }  
110.         }  
111.         T=Stack.top();  
112.         printf("%c",T->data);  
113.         Stack.pop();  
114.     }                                                                                                                                     
115. }  
116. void main()  
117. {  
118.     
119.     BiTree T;  
120.     CreateBiTree(T);  
121.     PreOrderTraverse(T);  
122.     printf("\n");  
123.          InOrderTraverse(T);  
124.     printf("\n");  
125.     PostOrderTraverse(T);  
126.     printf("\n");  
127. }