剑指offer（56）-按之字形顺序打印二叉树

题目描述

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请实现一个函数按照之字形打印二叉树，即第一行按照从左到右的顺序打印，第二层按照从右至左的顺序打印，第三行按照从左到右的顺序打印，其他行以此类推。

代码

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/*struct TreeNode {    int val;    struct TreeNode *left;    struct TreeNode *right;    TreeNode(int x) :            val(x), left(NULL), right(NULL) {    }};*/class Solution {public:    vector<vector<int> > Print(TreeNode* pRoot) {        vector<vector<int>> result;        stack<TreeNode*> stack1,stack2;        bool direction = true;        if (pRoot != NULL) {            stack1.push(pRoot);        }        struct TreeNode *node;        while (!stack1.empty() || !stack2.empty()) {            vector<int> data;            if (!stack1.empty()) {                while (!stack1.empty()) {                    node = stack1.top();                    stack1.pop();                    data.push_back(node->val);                    if (node->left != NULL) {                        stack2.push(node->left);                    }                    if (node->right != NULL) {                        stack2.push(node->right);                    }                }                result.push_back(data);            }else if (!stack2.empty()){                while (!stack2.empty()) {                    node = stack2.top();                    stack2.pop();                    data.push_back(node->val);                    if (node->right != NULL) {                        stack1.push(node->right);                    }                    if (node->left != NULL) {                        stack1.push(node->left);                    }                }                result.push_back(data);            }        }        return result;    }};