题解 | #按之字形顺序打印二叉树#

思路：层次遍历，并且在层次遍历过程中添加一个标志，调整每一层元素的顺序。

/*
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{};
        queue<TreeNode*> que{};
        if(pRoot==nullptr) return result;
        que.push(pRoot);
        int level=0;
        while(!que.empty()){
            int n=que.size();
            vector<int> temp{};
            for(int i=0;i<n;i++){
                auto node=que.front();
                temp.push_back(node->val);
                que.pop();
                if(node->left) que.push(node->left);
                if(node->right) que.push(node->right);
            }
            if(level%2==0) result.push_back(temp);
            else{
                reverse(temp.begin(),temp.end());
                result.push_back(temp);
            }
            level++;
        }
        return result;
    }
    
};