二叉树系列四：二叉树的遍历（非递归）

在二叉树系列三中讲述了二叉树的前序遍历、中序遍历和后序遍历的递归实现，可以看到采用递归实现的代码非常简单，但是代码简单不代表实际运行过程中也能达到最简。下面将要介绍二叉树几种遍历的非递归实现实现。

（1）前序遍历

 1 template<class T>
 2 void Tree<T>::PreOrderNonRec(TreeNode<T>* root)
 3 {
 4     if(root != NULL)
 5     {
 6         stack<TreeNode<T>*> s;
 7         TreeNode<T>* curr = root;
 8         while(curr || !s.empty())
 9         {
10             while(curr)
11             {
12                 cout<<curr->data<<endl;
13                 s.push(curr);
14                 curr = curr->leftChild;
15             }
16             if(!s.empty())
17             {
18                 curr = s.top();
19                 s.pop();
20                 curr = curr->rightChild;
21             }
22         }
23     }
24 }

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（2）中序遍历

 1 template<class T>
 2 void Tree<T>::MidOrderNonRec(TreeNode<T>* root)
 3 {
 4     if(root != NULL)
 5     {
 6         TreeNode<T>* curr = root;
 7         stack<TreeNode<T>*> s;
 8         while(curr || !s.empty())
 9         {
10             while(curr)
11             {
12                 s.push(curr);
13                 curr = curr->leftChild;
14             }
15             if(!s.empty())
16             {
17                 curr = s.top();
18                 s.pop();
19                 cout<<curr->data<<endl;
20                 curr = curr->rightChild;
21             }
22         }
23     }
24 }

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（3）后序遍历

 1 template<class T>
 2 struct StackItem
 3 {
 4     TreeNode<T>* node;
 5     bool RCVisited;
 6 };
 7 
 8 template<class T>
 9 void Tree<T>::PostOrderNonRec(TreeNode<T>* root)
10 {
11     if(root != NULL)
12     {
13         TreeNode<T>* curr = root;
14         stack<StackItem<T>> s;
15         StackItem<T> item;
16         while(curr || !s.empty())
17         {
18             while(curr)
19             {
20                 item.node = curr;
21                 item.RCVisited = false;
22                 s.push(item);
23                 curr = curr->leftChild;
24             }
25             if(!s.empty())
26             {
27                 item = s.top();
28                 s.pop();
29                 curr = item.node;
30                 if(item.RCVisited)
31                 {
32                     cout<<curr->data<<endl;
33                     curr = NULL;
34                 }
35                 else
36                 {
37                     item.RCVisited = true;
38                     s.push(item);
39                     curr = curr->rightChild;
40                 }
41             }
42         }
43     }
44 }

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posted on 2013-06-20 16:40 Sophia-呵呵小猪阅读(215) 评论(0) 编辑收藏举报