题解 | #按之字形顺序打印二叉树#

/**
 * struct TreeNode {
 *	int val;
 *	struct TreeNode *left;
 *	struct TreeNode *right;
 *	TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 * };
 */
#include <vector>
class Solution {
public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param pRoot TreeNode类 
     * @return int整型vector<vector<>>
     */
    vector<vector<int> > Print(TreeNode* pRoot) {
        // write code here
        if(pRoot==nullptr) return {};
        vector<vector<int> > res;
        queue<TreeNode*> que; //辅助队列
        que.push(pRoot); //根入队
        int n=que.size(); 
        int leftprintf=1; //从左向右
        vector<int> vec;
        while(!que.empty()){
            pRoot=que.front();
            que.pop();
            vec.push_back(pRoot->val);
            n--;
            if(pRoot->left) que.push(pRoot->left);
            if(pRoot->right) que.push(pRoot->right);
            if(n==0){
                if(leftprintf==-1){ 
                    reverse(vec.begin(),vec.end());
                }
                res.push_back(vec);
                vec.clear();
                leftprintf=-leftprintf; //下一层
                n=que.size(); 
            }
        }
        return res;
        
    }
};