剑指offer之分行从上到下之字行打印二叉树

1 问题

分行从上到下之字行打印二叉树

比如二叉树

                          2
                    3            5           
                 1     4      2      3       
              3    2 1   5  1   4  2   3   

 分行从上到下之字行打印二叉树结果如下

    2
    5       3
    1       4       2       3
    3       2       4       1       5       1       2       3


2 分析

这里我们可以用2个栈（先进后出），先把stack1push根节点，然后把stack全部弹出来，分别push根节点的左节点和右节点到stack2，然后stack2弹出栈里面的每个节点，我们分别把每个节点的右节点和左节点push到stack1,里面去，直到stack1和stack2都是空元素结束循环。

 
3 代码实现

    #include <iostream>
    #include <stack>
     
    using namespace std;
     
    typedef struct Node
    {
        int value;
        struct Node* left;
        struct Node* right;
    } Node;
     
     
    void layer_print(Node *head)
    {
        if (head == NULL)
        {
           std::cout << "head is NULL" << std::endl;
           return;
        }
        std::stack<Node *> stack1, stack2;
        stack1.push(head);
        while((stack1.size() != 0) || (stack2.size() != 0))
        {
                while (stack1.size() != 0)
            {
                Node *node = stack1.top();
                std::cout << node->value << "\t";
                if (node->left)
                    stack2.push(node->left);
                if (node->right)
                    stack2.push(node->right);
                stack1.pop();
            }
            std::cout << std::endl;
                    while (stack2.size() != 0)
            {
                Node *node = stack2.top();
                std::cout << node->value << "\t";
                if (node->right)
                    stack1.push(node->right);
                if (node->left)
                    stack1.push(node->left);
                stack2.pop();
            }         
                    std::cout << std::endl;
        }
    }
       
     
    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;
        layer_print(&head1);
        return 0;
    }

 
4 运行结果

    2
    5       3
    1       4       2       3
    3       2       4       1       5       1       2       3

 

 

作者：chen.yu
深信服三年半工作经验，目前就职游戏厂商，希望能和大家交流和学习,
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