C语言非递归实现二叉树的先序、中序、后序、层序遍历

C语言非递归实现二叉树的先序、中序、后序、层序遍历代码如下：

  1 #include <stdio.h>
  2 #include <stdlib.h>
  3 #include <stack>
  4 #include <queue>
  5 using namespace std;
  6
  7 //*****二叉树的二叉链表存储表示*****//
  8 typedef struct BiNode
  9 {
 10     char data;
 11     struct BiNode *lchild, *rchild;
 12     int visitCount;
 13 }BiNode, *BiTree;
 14
 15 //*****按先序次序输入二叉树中结点的值(一个字符)，空格字符表示空树构造二叉链表表示的二叉树T*****//
 16 void CreateBiTree(BiTree &T)
 17 {
 18     char ch;
 19     scanf("%c", &ch);
 20     if(ch == ‘ ‘)
 21     {
 22         T = NULL;
 23     }
 24     else
 25     {
 26         if(!(T = (BiNode *)malloc(sizeof(BiNode))))
 27         {
 28             return;
 29         }
 30         T->data = ch;                            //生成根结点
 31         T->lchild = NULL;
 32         T->rchild = NULL;
 33         CreateBiTree(T->lchild);                //构造左子树
 34         CreateBiTree(T->rchild);                //构造右子树
 35     }
 36
 37     return;
 38 }
 39
 40 //*****先序遍历二叉树*****//
 41 void PreOrderTraverse(BiTree T)
 42 {
 43     stack<BiTree> TreeStack;
 44     BiTree p = T;
 45
 46     while (p || !TreeStack.empty())
 47     {
 48         if (p)
 49         {
 50             printf("%c ", p->data);
 51             TreeStack.push(p);
 52             p = p->lchild;
 53         }
 54         else
 55         {
 56             p = TreeStack.top();
 57             TreeStack.pop();
 58             p = p->rchild;
 59         }
 60     }
 61 }
 62
 63 //*****中序遍历二叉树*****//
 64 void InOrderTraverse(BiTree T)
 65 {
 66     stack<BiTree> TreeStack;
 67     BiTree p = T;
 68
 69     while (p || !TreeStack.empty())
 70     {
 71         if (p)
 72         {
 73             TreeStack.push(p);
 74             p = p->lchild;
 75         }
 76         else
 77         {
 78             p = TreeStack.top();
 79             printf("%c ", p->data);
 80             TreeStack.pop();
 81             p = p->rchild;
 82         }
 83     }
 84 }
 85
 86 //*****后序遍历二叉树*****//
 87 void PostOrderTraverse(BiTree T)
 88 {
 89     stack<BiTree> TreeStack;
 90     BiTree p = T;
 91
 92     while (p || !TreeStack.empty())
 93     {
 94         if (p)
 95         {
 96             p->visitCount = 1;
 97             TreeStack.push(p);
 98             p = p->lchild;
 99         }
100         else
101         {
102             p = TreeStack.top();
103             TreeStack.pop();
104             if (p->visitCount == 2)
105             {
106                 printf("%c ", p->data);
107                 p = NULL;
108             }
109             else
110             {
111                 p->visitCount++;
112                 TreeStack.push(p);
113                 p = p->rchild;
114             }
115         }
116     }
117 }
118
119 //*****层序遍历二叉树*****//
120 void LevelOrderTraverse(BiTree T)
121 {
122     if (!T)
123     {
124         return;
125     }
126
127     queue<BiTree> TreeQueue;
128     TreeQueue.push(T);
129     BiTree p = T;
130     while (!TreeQueue.empty())
131     {
132         p = TreeQueue.front();
133         TreeQueue.pop();
134         printf("%c ", p->data);
135
136         if (p->lchild)
137         {
138             TreeQueue.push(p->lchild);
139         }
140         if (p->rchild)
141         {
142             TreeQueue.push(p->rchild);
143         }
144     }
145 }
146
147 int main(void)
148 {
149     BiTree T;
150     printf("请按先序次序输入二叉树中结点的值(字符)，空格字符表示空树:\n");
151     CreateBiTree(T);
152
153     printf("先序遍历结果为:");
154     PreOrderTraverse(T);
155     printf("\n\n");
156
157     printf("中序遍历结果为:");
158     InOrderTraverse(T);
159     printf("\n\n");
160
161     printf("后序遍历结果为:");
162     PostOrderTraverse(T);
163     printf("\n\n");
164
165     printf("层序遍历结果为:");
166     LevelOrderTraverse(T);
167     printf("\n\n");
168
169     return 0;
170 }

以如下二叉树为例，给出按先序次序输入二叉树中结点的值（字符），从而按照本文给出的算法构造二叉树。

输入字符的顺序是：-+a空格空格*b空格空格-c空格空格d空格空格/e空格空格f空格空格，即可验证本文提供的遍历算法。