二叉树的前序/中序/后续遍历（递归+非递归）

　　这几日又把二叉树的递归写了一遍，原来是用C写的，自己写了一个栈，这一次直接用的C++，使用了自带的栈结构。代码如下：

  1 /*************************************************************************
  2     > Author: Yves
  3     > E-mail: [email protected]
  4     > File Name: BiTreeNew.cpp
  5     > Description: ...
  6     > Created  Time: 2015-05-17. 15:51:24
  7     > Modified Time: 2015-05-17. 15:51:24
  8  ************************************************************************/
  9
 10 #include<stack>
 11 #include<cstdlib>
 12 #include<stdio.h>
 13 #include<iostream>
 14 using namespace std;
 15
 16 typedef char ElemType;
 17
 18 typedef struct tagBiTreeNode
 19 {
 20     ElemType data;
 21     struct tagBiTreeNode* leftChild;
 22     struct tagBiTreeNode* rightChild;
 23 }BiTreeNode, *pBiTreeNode;//指向BiTNode的指针
 24
 25 //创建二叉树
 26 static void CreatBiTree(pBiTreeNode *root);
 27 //访问树
 28 static void VisitTree(pBiTreeNode p, const int level);
 29 //前序递归遍历
 30 static void PreOrderRecursiveTraversal(const pBiTreeNode root, int level, void (*VisitTree)(pBiTreeNode p, const int level));
 31 //前序非递归遍历
 32 static void PreRecursiveTraversal(const pBiTreeNode root, void (*VisitTree)(pBiTreeNode p, const int level));
 33 //中序递归遍历
 34 static void InOrderRecursiveTraversal(const pBiTreeNode root, int level, void (*VisitTree)(pBiTreeNode p, const int level));
 35 //中序非递归遍历
 36 static void InOrdeTraversal(const pBiTreeNode root, void (*VisitTree)(pBiTreeNode p, const int level));
 37 //后序递归遍历
 38 static void PostOrderRecursiveTraversal(const pBiTreeNode root, int level, void (*VisitTree)(pBiTreeNode p, const int level));
 39 //后序非递归遍历
 40 static void PostOrderTraversal(const pBiTreeNode root, void (*VisitTree)(pBiTreeNode p, const int level));
 41
 42 static void CreatBiTree(pBiTreeNode *root)
 43 {
 44     /*Here we creat the tree in preorder, so the input
 45     sequences must comply with the preorder*/
 46     ElemType c;
 47     cin>>c;
 48     if(c != ‘#‘)
 49     {
 50     *root = (BiTreeNode*)malloc(sizeof(BiTreeNode));
 51         (*root)->data = c;
 52         CreatBiTree(&(*root)->leftChild);
 53         CreatBiTree(&(*root)->rightChild);
 54     }else
 55     {
 56         *root = NULL;
 57         return;
 58     }
 59 }
 60
 61 static void VisitTree(pBiTreeNode p, const int level)
 62 {
 63     if(level > 0)
 64     {
 65         cout<<p->data<<" is on the level "<<level<<"."<<endl;
 66     }
 67     else
 68     {
 69         cout<<p->data<<" ";
 70     }
 71 }
 72
 73 static void PreOrderRecursiveTraversal(const pBiTreeNode root, int level, void (*VisitTree)(pBiTreeNode p, const int level))
 74 {
 75     if(root == NULL)
 76     {
 77         return;
 78     }
 79     VisitTree(root, level);
 80     PreOrderRecursiveTraversal(root->leftChild, level + 1, VisitTree);
 81     PreOrderRecursiveTraversal(root->rightChild, level + 1, VisitTree);
 82 }
 83 static void PreRecursiveTraversal(const pBiTreeNode root, void (*VisitTree)(pBiTreeNode p, const int level))
 84 {
 85     if(root == NULL)
 86     {
 87         return;
 88     }
 89     stack<pBiTreeNode> s;
 90     pBiTreeNode p;
 91     p = root;
 92     while(!s.empty() || p != NULL)
 93     {
 94         while(p != NULL)
 95         {
 96             VisitTree(p, 0);
 97             s.push(p);
 98             p = p->leftChild;
 99         }
100         if(!s.empty())
101         {
102             p = s.top();
103             s.pop();
104             p = p->rightChild;
105         }
106     }
107 }
108 static void InOrderRecursiveTraversal(const pBiTreeNode root,int level, void (*VisitTree)(pBiTreeNode p, const int level))
109 {
110     if(root == NULL)
111     {
112         return;
113     }
114     InOrderRecursiveTraversal(root->leftChild, level + 1, VisitTree);
115     VisitTree(root, level);
116     InOrderRecursiveTraversal(root->rightChild, level + 1, VisitTree);
117 }
118 static void InOrderTraversal(const pBiTreeNode root, void (*VisitTree)(pBiTreeNode p, const int level))
119 {
120     if(root == NULL)
121     {
122         return;
123     }
124     stack<pBiTreeNode> s;
125     pBiTreeNode p;
126     p = root;
127     while(!s.empty() || p != NULL)
128     {
129         while(p != NULL)
130         {
131             s.push(p);
132             p = p->leftChild;
133         }
134         if(!s.empty())
135         {
136             p = s.top();
137             VisitTree(p, 0);
138             s.pop();
139             p = p->rightChild;
140         }
141     }
142 }
143 static void PostOrderRecursiveTraversal(const pBiTreeNode root,int level, void (*VisitTree)(pBiTreeNode p, const int level))
144 {
145     if(root == NULL)
146     {
147         return;
148     }
149     PostOrderRecursiveTraversal(root->leftChild, level + 1, VisitTree);
150     PostOrderRecursiveTraversal(root->rightChild, level + 1, VisitTree);
151     VisitTree(root, level);
152 }
153 static void PostOrderTraversal(const pBiTreeNode root, void (*VisitTree)(pBiTreeNode p, const int level))
154 {
155     stack<pBiTreeNode> s;
156     pBiTreeNode pCurrentNode;
157     pBiTreeNode pPrecedingNode = NULL;
158     s.push(root);
159     while(!s.empty())
160     {
161         pCurrentNode = s.top();
162         /*There is two cases:
163         * 1, the lefechild and the rightchild is all NULL, meaning it is a leaf node,so we can visit it directly.
164         * 2, the preceding node is not NULL,in addtion, it is the rightchild or the leftchild of the curretn node.
165         * Notice because of our order of pushing nodes into stack, it is sure that the two nodes(leftchild,rightchild)
166         * have accessed yet if one of conditions satisfies:
167         *          pPrecedingNode == pCurrentNode->leftChild  or
168         *          pPrecedingNode == pCurrentNode->rightChild))
169         * of course, pPrecedingNode != NULL must be satisfied.
170         */
171         if((pCurrentNode->leftChild == NULL && pCurrentNode->rightChild == NULL)
172             || (pPrecedingNode != NULL && (pPrecedingNode == pCurrentNode->leftChild
173                     || pPrecedingNode == pCurrentNode->rightChild)))
174         {
175             VisitTree(pCurrentNode, 0);
176             s.pop();
177             pPrecedingNode = pCurrentNode;
178         }else
179         {
180             if(pCurrentNode->rightChild != NULL)
181             {
182                 s.push(pCurrentNode->rightChild);
183             }
184             if(pCurrentNode->leftChild != NULL)
185             {
186                 s.push(pCurrentNode->leftChild);
187             }
188         }
189     }
190 }
191
192
193 int main(void)
194 {
195     pBiTreeNode root;
196
197     cout<<"Please input the node of the tree(preorder sequence):  "<<endl;
198     CreatBiTree(&root);
199     cout<<endl;
200
201
202     cout<<"Traverse the tree in preorder(non-recursive):  "<<endl;
203     PreRecursiveTraversal(root, &VisitTree);
204     cout<<endl;
205     cout<<"Traverse the tree in preorder:  "<<endl;
206     PreOrderRecursiveTraversal(root,1,&VisitTree);
207     cout<<endl;
208
209
210     cout<<"Traverse the tree in inorder(non-recursive):  "<<endl;
211     InOrderTraversal(root, &VisitTree);
212     cout<<endl;
213     cout<<"Traverse the tree in inorder:  "<<endl;
214     InOrderRecursiveTraversal(root, 1, &VisitTree);
215     cout<<endl;
216
217     cout<<"Traverse the tree in postorder(non-recursive):  "<<endl;
218     PostOrderTraversal(root, &VisitTree);
219     cout<<endl;
220     cout<<"Traverse the tree in posteorder:  "<<endl;
221     PostOrderRecursiveTraversal(root, 1, &VisitTree);
222     cout<<endl;
223
224     return 0;
225 }