剑指offer之中序打印二叉树（非递归实现）

1 问题

中序打印二叉树（非递归实现），比如二叉树如下

  

   

    

     

    
    

     
 /* 2
     
    
   

    

     

    
    

     
 * 3 5 
     
    
   

    

     

    
    

     
 * 1 4 2 3 
     
    
   

    

     

    
    

     
 * 3 2 1   5  1   4  2   3  
     
    
  
 

中序：按左中右来打印二叉树，结果如下

  

   

    

     

    
    

     

      3
     
    
   

    

     

    
    

     

      1
     
    
   

    

     

    
    

     

      2
     
    
   

    

     

    
    

     

      3
     
    
   

    

     

    
    

     

      1
     
    
   

    

     

    
    

     

      4
     
    
   

    

     

    
    

     

      5
     
    
   

    

     

    
    

     

      2
     
    
   

    

     

    
    

     

      1
     
    
   

    

     

    
    

     

      2
     
    
   

    

     

    
    

     

      4
     
    
   

    

     

    
    

     

      5
     
    
   

    

     

    
    

     

      2
     
    
   

    

     

    
    

     

      3
     
    
   

    

     

    
    

     

      3
     
    
  
 

2 代码实现

  

   

    

     

    
    

     

      #include <iostream>
     
    
   

    

     

    
    

     

      #include <stack>
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     

      using namespace std;
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     

      typedef struct Node
     
    
   

    

     

    
    

     

      {
     
    
   

    

     

    
    

     
 int value;
     
    
   

    

     

    
    

     
 struct Node* left;
     
    
   

    

     

    
    

     
 struct Node* right;
     
    
   

    

     

    
    

     

      } Node;
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     

      void center_print(Node *head)
     
    
   

    

     

    
    

     

      {
     
    
   

    

     

    
    

     
	if (head == NULL)
     
    
   

    

     

    
    

     

      	{
     
    
   

    

     

    
    

     
		std::cout << "head is NULL" << std::endl;
     
    
   

    

     

    
    

     
		return;
     
    
   

    

     

    
    

     

      	}
     
    
   

    

     

    
    

     
	std::stack<Node *> stack;
     
    
   

    

     

    
    

     
	Node *p = head;
     
    
   

    

     

    
    

     
	while (p != NULL || !stack.empty())
     
    
   

    

     

    
    

     

      	{
     
    
   

    

     

    
    

     
		while (p != NULL)
     
    
   

    

     

    
    

     

       {
     
    
   

    

     

    
    

     
 stack.push(p);
     
    
   

    

     

    
    

     
 p = p->left;
     
    
   

    

     

    
    

     

       }
     
    
   

    

     

    
    

     
 if (!stack.empty())
     
    
   

    

     

    
    

     

       {
     
    
   

    

     

    
    

     
 p = stack.top();
     
    
   

    

     

    
    

     
 std::cout << p->value << std::endl;
     
    
   

    

     

    
    

     
 stack.pop();
     
    
   

    

     

    
    

     
 p = p->right;
     
    
   

    

     

    
    

     

       }
     
    
   

    

     

    
    

     

      	} 
     
    
   

    

     

    
    

     

      } 
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     

      int main()
     
    
   

    

     

    
    

     

      {
     
    
   

    

     

    
    

     
 /* 2
     
    
   

    

     

    
    

     
 * 3 5 
     
    
   

    

     

    
    

     
 * 1 4 2 3 
     
    
   

    

     

    
    

     
 * 3 2 1   5  1   4  2   3   
     
    
   

    

     

    
    

     
 */
     
    
   

    

     

    
    

     
 Node head1, node1, node2, node3, node4, node5, node6;
     
    
   

    

     

    
    

     
 Node node7, node8, node9, node10, node11, node12, node13, node14;
     
    
   

    

     

    
    

     
 head1.value = 2;
     
    
   

    

     

    
    

     
 node1.value = 3;
     
    
   

    

     

    
    

     
 node2.value = 5;
     
    
   

    

     

    
    

     
 node3.value = 1;
     
    
   

    

     

    
    

     
 node4.value = 4;
     
    
   

    

     

    
    

     
 node5.value = 2;
     
    
   

    

     

    
    

     
 node6.value = 3;
     
    
   

    

     

    
    

     
 node7.value = 3;
     
    
   

    

     

    
    

     
 node8.value = 2;
     
    
   

    

     

    
    

     
 node9.value = 1;
     
    
   

    

     

    
    

     
 node10.value = 5;
     
    
   

    

     

    
    

     
 node11.value = 1;
     
    
   

    

     

    
    

     
 node12.value = 4;
     
    
   

    

     

    
    

     
 node13.value = 2;
     
    
   

    

     

    
    

     
 node14.value = 3;
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
 head1.left = &node1;
     
    
   

    

     

    
    

     
 head1.right = &node2;
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
 node1.left = &node3;
     
    
   

    

     

    
    

     
 node1.right = &node4;
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
 node2.left = &node5;
     
    
   

    

     

    
    

     
 node2.right = &node6;
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
 node3.left = &node7;
     
    
   

    

     

    
    

     
 node3.right = &node8;
     
    
   

    

     

    
    

     
 node4.left = &node9;
     
    
   

    

     

    
    

     
 node4.right = &node10;
     
    
   

    

     

    
    

     
 node5.left = &node11;
     
    
   

    

     

    
    

     
 node5.right = &node12;
     
    
   

    

     

    
    

     
 node6.left = &node13;
     
    
   

    

     

    
    

     
 node6.right = &node14;
     
    
   

    

     

    
    

     
   
     
    
   

    

     

    
    

     
 node7.left = NULL;
     
    
   

    

     

    
    

     
 node7.right = NULL;
     
    
   

    

     

    
    

     
 node8.left = NULL;
     
    
   

    

     

    
    

     
 node8.right =  NULL;
     
    
   

    

     

    
    

     
 node9.left = NULL;
     
    
   

    

     

    
    

     
 node9.right = NULL;
     
    
   

    

     

    
    

     
 node10.left = NULL;
     
    
   

    

     

    
    

     
 node10.right = NULL;
     
    
   

    

     

    
    

     
 node11.left = NULL;
     
    
   

    

     

    
    

     
 node11.right = NULL;
     
    
   

    

     

    
    

     
 node12.left = NULL;
     
    
   

    

     

    
    

     
 node12.right = NULL;
     
    
   

    

     

    
    

     
 node13.left = NULL;
     
    
   

    

     

    
    

     
 node13.right = NULL;
     
    
   

    

     

    
    

     
 node14.left = NULL;
     
    
   

    

     

    
    

     
 node14.right = NULL;
     
    
   

    

     

    
    

     
 center_print(&head1);
     
    
   

    

     

    
    

     
 return 0;
     
    
   

    

     

    
    

     

      }
     
    
  
 

3 运行结果

  

   

    

     

    
    

     

      2
     
    
   

    

     

    
    

     

      3
     
    
   

    

     

    
    

     

      1
     
    
   

    

     

    
    

     

      3
     
    
   

    

     

    
    

     

      2
     
    
   

    

     

    
    

     

      4
     
    
   

    

     

    
    

     

      1
     
    
   

    

     

    
    

     

      5
     
    
   

    

     

    
    

     

      5
     
    
   

    

     

    
    

     

      2
     
    
   

    

     

    
    

     

      1
     
    
   

    

     

    
    

     

      4
     
    
   

    

     

    
    

     

      3
     
    
   

    

     

    
    

     

      2
     
    
   

    

     

    
    

     

      3
     
    
  
 

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原文链接：chenyu.blog.csdn.net/article/details/90350060